University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

Public Health Resources Public Health Resources

7-1962 Organic Phosphorus Poisoning and Its Therapy William F. Durham U.S. Department of Health, Education, and Welfare

Wayland J. Hayes Jr. U.S. Department of Health, Education, and Welfare

Follow this and additional works at: http://digitalcommons.unl.edu/publichealthresources

Durham, William F. and Hayes, Wayland J. Jr., "Organic Phosphorus Poisoning and Its Therapy" (1962). Public Health Resources. 531. http://digitalcommons.unl.edu/publichealthresources/531

This Article is brought to you for free and open access by the Public Health Resources at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Public Health Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 11-031 21

Organic Phosphorus Poisoning and Its Therapy PUBLICATION With Special Reference to Modes of Action and Compounds That 107 Reactivate Inhibited Cholinesterase TOXICOl.OGY PROGRAM WILLIAM F. DURHAM, Ph.D., AND WAYLAND J. HAYES, JR., M.D., Ph.D., ATLANTA TeChnology Brant'h . COmmunicable Disease Cont''t'' Atlanta 22, Ga. Contents This therapy produces relief of symptoms Introduction based on blocking the action of excess acetyl­ Nature and Physiologic Function of Cholinesterase choline. Symptoms of Organic Phosphorus Poisoning Mechanism of Inhibition of Cholinesterase More recently, a number of specific anti­ Measurement of Cholinesterase Activity and Its dotes have been developed which act to repair Relationship to Symptomatology the basic biochemical lesion in organic phos­ Measurement of Metabolites and Their Relationship phorus poisoning by freeing the cholinester­ to Symptomatology Use and Action of Atropine and Other Nonspecific ase from its combination with the inhibitor. Antidotes In the present paper, some of the pertinent Development of Specific Antidotes background material relative to' organic phos­ Chemical and Physiologic Properties of Oximes phorus poisoning will be reviewed, and the Antidotal Efficacy of Oximes in Poisoned Experimental Animals properties and usage of these specific anti­ Application of 2-PAM in Poisoning in Man dotes will be discussed in some detail. Em­ Suggestions for Treatment phasis will be given to those aspects of Prevention of Poisoning symptomatology and treatment which might Comment and Summary be of most value to the physician faced with Introduction a presumptive case of poisoning. Organic phosphorus compounds are of Nature and Physiologic Function considerable interest and importance by vir­ of Cholinesterase ture of their widespread use as insecticides; their effectiveness in the treatment of my­ There are 2 general types of cholinesterase asthenia gravis, glaucoma, and abdominal present in the animal organism.9 These are: distention; and their potential application as ( 1) the true, specific enzyme, acetylcholin­ war gases. These compounds owe their esterase, which has an almost specific affinity pharmacologic effect primarily, if not entire­ for the naturally occurring substrate acetyl­ ly, to their ability to inhibit the enzyme choline, although it will hydrolyze several cholinesterase with a resultant overstimula­ synthetic esters; and (2) the nonspecific tion of the parasympathetic nervous system enzyme, pseudocholinesterase, which has the by the acetylcholine which accumulates. ability to hydrolyze quite a wide range of Atropine has been the drug of choice for the naturally occurring and synthetic esters in addition to acetylcholine. Acetylcholinester­ treatment of organophosphorus poisoning. ase occurs in the nervous system, where it is Submitted for publication Dec. 12, 1961. of great functional importance; in muscles; From the Toxicology Section, Technology Branch, and in glands; and it also occurs incidentally Communicable Disease Center, Public Health Service, U.S. Department of Health, Education, in erythrocytes. The pseudoenzyme is found and Welfare, Wenatchee, Wash. (Dr. Durham) and in the blood plasma and in various tissues, Atlanta (Dr. Hayes). including the central nervous system. 22 ARCHIVES OF ENVIRONMENTAL HEALTH

In addition to location and substrate speci­ muscle; and probably (4) from certain struc­ ficity, there are other differences between tures within the central nervous system. true and pseudocholinesterases. The latter Normally, in the presence of the usual con­ functions well in the presence of an excess centration of cholinesterase, the acetylcholine of substrate, while the former is inhibited formed during the process of transmission under this condition. A number of inhibitors is hydrolyzed almost instantly so that the show considerable specificity for 8ne type of synapse is again ready to transmit a physio­ enzyme. For example, diisopropyl fluorophos­ logic impulse. A small abnormal accumula­ phate (DFP) in low concentrations is almost tion of acetylcholine at the synapse or completely specific for pseudocholinester­ myoneural junction produces an abnormal ase. 73 increase in function (e.g., fasciculation of It has been suggested that certain direct muscle), while greater accumulation rapidly effects of the anticholinesterase organic produces a decrease in function (e.g., paral­ phosphorus compounds do not depend on ysis). A decrease in cholinesterase activity inhibition of cholinesterase.w5 Von Kaulla is accompanied by an accumulation of acetyl­ and Holmes 142 have reported that patients choline. The symptoms caused by organic poisoned by organic phosphorus compounds phosphorus poisoning are, therefore, very show abnormalities in the blood-clotting similar to those resulting from overstimula­ mechanism, but the changes were in both tion of the parasympathetic nervous system. directions from normal and must be consid­ ered unconfirmed. Some of the compounds Symptoms of Organic do produce a delayed reaction similar to Phosphorus Poisoning "J ake-Ieg paralysis," 11,41,94 but the clinical Absorption of the organic phosphorus picture is quite distinct from that of ordinary anticholinesterases may occur through the poisoning. Although any statement about the lungs, gastrointestinal tract, or skin. Absorp­ relationship between cholinesterase inhibition tion of these materials is more rapid and and the classical picture of poisoning must be more complete through the former 2 routes qualified in terms of the rate of depression, than through the latter. Respiratory exposure the degree of depression, and perhaps other may be of predominant importance wherever factors, the evidence for a lack of relation­ there is a sufficient concentration of vapor ship is indefinite. On the contrary, the evi­ or of aerosol fine enough to inhale. However, dence for a lack of relationship between in many agricultural and public health usages, cholinesterase inhibition and paralytic effect workers get contamination predominantly on is much more clear. In spite of these excep­ their skins.13,3o,42 The oral route of 'exposure tions, it is true that the predominant pharma­ occurs in accidental poisoning (particularly cologic effect of the organic phosphorus of children), in murder, and in suicide. In­ compounds is inhibition of the enzyme acetyl­ gestion has not been considered of impor­ cholinesterase. tance in occupational exposurt; but a case In order to have an understanding of the has been reported in which a parathion spray­ action of acetylcholinesterase and of the man became severely poisoned, presumably effect of its inhibition on the animal organ­ from eating a candy bar which he had been ism, it is first necessary to look at the physio­ carrying for 6 hours in an open outside logic action of acetylcholine. Acetylcholine is pocket of his work clothes.120 the chemical mediator of the parasympathetic Although many of the organic phosphorus nervous system and is necessary for trans­ compounds have a high acute toxicity, agri­ mission of the nervous impulse (1) from cultural residues of these materials on food preganglionic fibers to autonomic ganglia; have not been a problem, due to their rapid (2) from postganglionic, cholinergic nerves breakdown and the fact that they are not to smooth and cardiac muscle and to secre­ stored in the animal body.40 Direct contami­ tory cells: (3) from motor nerves to striated nation of food by concentrated formulations Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 23

of these insecticides during shipment has lacrimation, profuse sweating, pallor, and been the cause of several outbreaks of poison­ dyspnea. In some subjects there is audible ing in other countries. wheezing. More severe signs and symptoms The symptom picture in organic phos­ include involuntary defecation and urination, phorus poisoning may vary in severity, in excessive bronchial secretions, and (accord­ rapidity of onset, in duration, and in range, ing to some authors) pulmonary edema. depending upon the route and the magnitude Nicotine-like effects appear usually after of exposure. Minor exposure to a vapor or the muscarine-like effects have reached mod­ aerosol of a direct inhibitor of cholinesterase erate severity. These include muscle twitch­ may produce local effects on the eye or re­ ing, fasciculations, and cramps. At about the spiratory system through local absorption same time, there appears increased fatigabil­ and without systemic effect. The optic effects ity and mild, generalized weakness which is consist of miosis, a sensation of pressure in increased by exertion. Extensive exposure or behind the eye, headache, and conjunctival produces severe weakness, including weak­ hyperemia. Unilateral manifestation of these ness of the muscles of respiration. There may optic effects has been implicated in visual be a mild or moderate elevation of blood difficulties experienced by pilots applying pressure. these materials.140 The local effects on the The central-nervous-system effects include respiratory tract involve increased secretion, tension, anxiety, restlessness, giddiness, and a feeling of tightness in the chest, and emotional lability. Late effects include in­ occasionally wheezing. Localized massive somnia, excessive dreaming, and occasionally dermal exposure can lead to muscular fas­ nightmares. Greater exposure produces head­ ciculation and sweating confined to the area ache, tremor, drowsiness, difficulty in con­ of absorption. centration, slowness of recall, and confusion. Systemic effects may follow absorption by There may be withdrawal and depression. any route. If there has been adequate ex­ In the absence of symptoms, there is no posure to a vapor or aerosol, the local respira­ change in the electroencephalogram {EEG).66 tory effects already described will appear, Mild symptoms are accompanied by a slight but they will be rapidly followed by more diminution in potential, and moderate symp­ severe optic and respiratory distress and toms are accompanied by irregularity of by systemic manifestations. Dixon 38 has rhythm, variation and increase of potential, pointed out that too much reliance should and bursts of abnormal waves more or less not be placed on miosis as a diagnostic sign, reminiscent of waves seen in epileptics.107 since some poisoning cases, at least early in Lethal or near-lethal doses produce ataxia, their course, do not exhibit miosis, and a few slurring of words, multiple repetition of even have mydriasis. the last syllable of words, coma, areflexia, In systemic poisoning, the muscarine-like Cheyne-Stokes breathing, and finally, re­ effects are usually first to appear. They in­ spiratory arrest. clude anorexia, nausea, sweating, epigastric The cause of death may usually be at­ and substernal tightness (probably due to tributed to interference with respiration.66 cardiospasm), heartburn, belching, and tight­ Animal experiments have proved that the ness in the chest. The sequence of symptoms anticholinesterase organic phosphorus com­ varies somewhat with the route of exposure pounds interfere with respiration in at least -gastrointestinal effects usually being ear­ 4 ways, including bronchoconstriction, ex­ liest after ingestion; sweating, and at times cessive respiratory secretion, failure of the muscular fasciculations, after dermal ex­ muscles of respiration, and depression of the posure; and respiratory effects after inhala­ respiratory center. Although the respiratory tion. More severe exposure by whatever center is at first stimulated by anoxia of route produces abdominal cramps, increased whatever cause, it is rapidly depressed by peristalsis, vomiting, diarrhea, salivation, continued anoxia. The severe bronchial con- Durham-Hayes 24 ARCHIVES OF ENVIRONMENTAL HEALTH striction seen in animals following exposure the enzyme protein contains 2 active centers, to parathion or nerve gas has not been seen an "anionic site" and a "cationic or esteratic in man.66 The difference may depend on the site." The former, by means of coulombic different amount of bronchial musculature forces, attracts the positively charged qua­ in different species. ternary nitrogen atom of acetylcholine and The compounds also produce bradycardia thereby fixes and orients the substrate in a and various degrees of A-V block. If these proper position so that the esteratic site can effects are prevented by atropine, and if the exert its hydrolytic effect. The esteratic site animal is prevented from a respiratory death is thought to consist of a hydrogen-bonding by artificial respiration, it will eventually group which anchors the ester end of the succumb to a sufficient dose through dysfunc­ acetylcholine molecule. It has been suggested tion of the heart. This dysfunction will take that the ester-anchoring group may be the the form of ventricular fibrillation if atropine iminazole ring of histidine and that any phos­ should be administered in the presence of phoryl group which becomes attached here severe anoxia.1l;7 Even if atropine is given is subsequently transferred to an adjacent correctly, bradycardia and perhaps impaired serine moiety of the enzyme molecule by a contractility appear shortly before asystole N~O shift. It is thought that the effect of in the animal maintained by artificial respira­ change in pH on the hydrolytic activity of tion.83 Unanesthetized dogs, unlike anes­ this enzyme is mediated through changes in thetized ones, exposed to sarin by various ionization at these 2 sites. routes generally show bradycardia, increase In the following stage of the physiologic in pulse amplitude, decrease in oxygen ten­ reaction, the acetylcholine is split into choline sion, increase in carbon dioxide tension, and which is set free and the acetyl moiety which fall in arterial blood pH before changes in remains affixed to the enzyme. However, the respiratory rate and volume are evident.l;8.5lJ acetylated enzyme is unstable and easily The local effects of organic phosphorus breaks down to form active enzyme and exposure begin within a few minutes after acetic acid. exposure and last for periods ranging from The reaction between enzyme and organic several hours to a day, except that miosis may phosphorus inhibitor is thought to involve last 2 to 5 days or occasionally longer. Mod­ only the esteratic site, except with the phos­ erate systemic effects begin within about half phorylcholines 57 that are used as laboratory an hour after respiratory exposure, three­ tools only and need not be discussed further. quarters of an hour after oral exposure, and This center is phosphorylated to form a com­ 2 to 3 hours after dermal exposure. With plex which is, at least by contrast with the sufficient exposure, the onset of symptoms is acetylated enzyme, quite stable. The phos­ essentially instantaneous, with death in a few phorylation is thought to proceed in 2 stages, minutes. Moderately severe symptoms may as discussed in detail below under "Chemical not reach their maximum until 4 to 8 hours and Physiologic Properties of Oximes." The after onset; they diminish over a period of stability of this phosphorylated enzyme ac­ 1 to 6 days. However, EEG changes may counts for the fact that organic phosphorus persist for 11 to 18 days.66 compounds are inhibitors rather than sub­ strates for cholinesterase. During this inhibi­ Mechanism of Inhibition tion reaction, the anionic site remains of Cholinesterase uninvolved. In recent years, much has been learned about the molecular forces involved in the Measurement of Cholinesterase interaction of acetylcholinesterase both with Activity and Its Relationship its natural substrate and with organic phos­ to Symptomatology phorus inhibitors.111 Wilson and Berg­ Cholinesterase activity can be determined mann 153 have postulated that the surface of by any of several methods based on: (l) di- Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 25

rect or indirect measurement of the acetic ence suggests that small multiple exposures acid or other moiety released by hydrolysis over an extended period are not indefinitely of acetylcholine or other esters, or (2) direct cumulative in their effects but that the cholin­ measurement of acetylcholine remaining esterase level reaches a plateau.74,135 There after partial hydrolysis. is some evidence that the rate of inactivation The electrometric method of Michel 107 to­ of tissue cholinesterase, as well as the degree gether with a micromodification of this tech­ of inhibition, may influence the level of tissue nique for use with capillary blood samples 104 enzyme activity at which symptoms begin. is probably the most widely used method. The cholinesterase activity of the red blood There are also available colorimetric,W6 titri­ cells may be gradually depressed to near zero metric,18 and manometric 1 procedures. The by repeated exposure over a period of weeks colorimetric screening method of Limperos without systemic symptoms necessarily en­ and Ranta 100 is adaptable to the approximate suing, or without any relation to the severity determination of large numbers of samples of symptoms that occur.127,135 under field conditions. Other procedures in­ Following exposure, the blood enzymes, volve use of the Hestrin method 75 for meas­ especially the erythrocyte cholinesterase, re­ urement of acetylcholine. main at a low level of activity for some time The restoration of plasma or of plasma after the disappearance of symptoms. This and red blood cell cholinesterase activity may lag is thought by some to indicate that cholin­ be increased by plasma or whole blood trans­ esterase activity is restored more rapidly in fusions in animals without any effect on the the tissues than in the blood, although the symptoms of poisoning or appreciable re­ tissue regeneration rate is not fully known. duction in the susceptibility to further ex­ Chronic-feeding and certain other studies posure.14 indicate that the phenomenon may be ac­ Although the acetylcholinesterase of red counted for by tolerance rather than by a blood cells and the more general esterase of difference of recovery rate for different en­ the plasma are not directly related to the zymes.127 The adaptation to constant concen­ signs and symptoms of organic phosphorus trations of acetylcholine that has been poisoning, these enzymes are inhibited in a demonstrated to occur in ganglia 98 may well manner essentially parallel to the inhibition occur in other parts of the nervous system. of acetylcholinesterase of nerve, muscle, and This adaptation almost certainly contributes gland. The blood enzyme levels, and partic­ to the lack of parallelism between symptom­ ularly that of the erythrocytes, may be used atology and cholinesterase level. as an index of tissue enzyme levels. The It is true that effects of doses of anticholin­ erythrocyte cholinesterase level has been esterase compounds near the fatal level are shown to correlate rather closely with the partially cumulative if the doses are repeated activity of this enzyme in the brain during at relatively brief intervals. Thus, Callaway both poisoning and recovery in the rat.60 and Davies 21 have found in rabbits and Following a single exposure, maximum de­ guinea pigs that lowering the blood cholin­ pression of blood cholinesterase occurs within a few hours. The degree of depression esterase level to 50% of normal by either a varies with the amount of absorption, the single dose or repeated doses of tetraethyl logarithm of the fraction of enzyme inhibited pyrophosphate (TEPP) or sarin results in being proportional to the amount of toxicant an increased susceptibility of the animal to absorbed in connection with essentially in­ these agents. stantaneous dosage. Of course, absorption is Plasma cholinesterase is formed by the influenced by route, often being prolonged liver. Following cessation of exposure, plas­ for hours or even days after skin exposure. ma enzyme activity is increased by about Multiple exposures over a brief period are 13% of original activity during the first day, partially cumulative in their effect. Experi- and more slowly thereafter, so that 30 to 40 Durham-Hayes 26 ARCHIVES OF ENVIRONMENTAL HEALTH

days are required to reach the normal pre­ anticholinesterase organic phosphorus com­ exposure level. pounds have an increased tolerance for atro­ Once fully inhibited, the enzyme content pine. Furthermore, a single dose of as much of a particular erythrocyte is not regenerated. as lO mg. of atropine has been inadvertently Rather, in the absence of treatment with administered intravenously to normal adults oximes, the rate of regeneration of red­ without endangering life, although it has, of blood-cell cholinesterase reflects the replace­ course, produced very marked signs of over­ ment of red corpuscles in the circulation and dose. In the presence of severe anticholines­ thus requires 90 to 100 days to return to terase poisoning, 40 mg. of atropine may be original activity after nearly complete depres­ given in a day without producing symptoms sion. Regeneration occurs at a regular rate of overatropinization. The low toxicity of of about 1% of normal per day. atropine and its effectiveness in the treatment Barstad 12 concluded that respiratory func­ of anticholinesterase intoxication have been tion should be only slightly impaired by a discussed by Gordon and Frye.65 peripheral cholinesterase inhibition ap­ Severe symptoms of organic phosphorus proaching 90% and that consequently a poisoning should be treated by the physician rather slight degree of cholinesterase reac­ with the intravenous injection of 2 to 4 mg. tivation at the critical site should be sufficient of atropine. The effects of intravenous atro­ to relieve the peripheral failure of respira­ pine begin in 1 to 4 minutes and are maximal tory movements during poisoning with anti­ within 8 minutes. If muscarine-like symp­ cholinesterase agents. toms are not relieved, and if signs of atropin­ ization (dry, flushed skin and tachycardia) Measurement of Metabolites do not appear, the intravenous injection of and Their Relationship atropine in doses of 2 mg. should be repeated to Symptomatology at 5- to lO-minute intervals until symptoms Exposure to those organic phosphorus are relieved or signs of atropine overdosage compounds which, on hydrolysis, form appear. A mild degree of atropinization p-nitrophenol or one of its congeners can should be maintained in all cases for 24 hours be estimated by determination of these phe­ and in severe cases for at least 48 hours. nolic compounds in urine.45 Although ap­ Atropine should not be given to an anoxic plicable to a restricted group of compounds, patient because of the danger of producing this test has proved to be a more sensitive ventricular fibrillation. In the cyanotic pa­ measure of absorption than is cholinesterase tient, artificial respiration, oxygen, or other inhibition.4 A urine test based on excretion indicated measures should be carried out first of organically-bound phosphorus would be to correct the anoxia, and then atropine desirable, since metabolites of this type are, should be given. of course, common to all the compounds in Atropine should not be administered for this group. preventive purposes in persons who antici­ pate exposure to anticholinesterase agents. Use and Action of Atropine and Its use in this manner may mask the early Other Nonspecific Antidotes occurrence of signs and symptoms of intoxi­ Until recently, the most important factors cation and allow the patient to expose himself influencing survival after otherwise lethal to dangerous levels of the toxicant without cholinesterase inhibition appear to be prompt warning. Wills 145 has noted that animals administration of atropine in sufficient dos­ given atropine before respiratory exposure age and artificial respiration, if required.61 to sarin 'vapor were somewhat more sus­ The suggested dose of atropine is 2 mg. ceptible to the poison than controls given no initially, and as much as 6 mg. may safely be antidote. The ineffectiveness of atropine in given within lO minutes or more without this situation was interpreted as being due medical supervision. Individuals poisoned by to its action to prevent the bronchoconstric- Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 27 tion which otherwise occurs to some degree certain actions of the excess acetylcholine after inhalation of nerve gas vapor (see already accumulated. Atropine has no action "Symptoms of Organic Phosphorus Poison­ on the nicotonic effects of acetylcholine, in­ ing" ), there fore resulting in greater inhala­ cluding the neuromuscular block that leads tion and absorption from the respiratory to muscle weakness, and may finally end in tract. Patients who are sick enough to receive death due to paralysis of the respiratory mus­ atropine should be hospitalized and kept un­ cles.14li Although atropine specifically blocks der careful observation for 24 hours; in some the muscarinic actions of acetylcholine, it is instances, a marked improvement has been less effective in blocking certain muscarinic noted after atropine followed later by de­ actions (such as those on the intestine and terioration of the patient's condition, requir­ urinary bladder) than others (such as cardiac ing further treatment promptly.71 slowing and sialorrhea). The effects of anti­ Ocular symptoms produced by local ab­ cholinesterases on the central nervous system sorption do not respond to the systemic ad­ are reversed by atropine, and the increased ministration of atropine but are relieved by electrical activity of the brain, as shown by the local administration of 2% homatropine the EEG, is returned to normal.1li7 or, if severe, by the local administration of Tests with various synthetic parasympa­ 0.5% or 1% atropineYi7 Parenteral atropine tholytic agents, including l-N-butylscopolam­ may relieve miosis, but the effect is both ir­ monium bromide (Buscopan) ,37 have not regular and transient. I f local ocular effects shown any of these compounds to be signif­ are present, the size of the pupils obviously icantly more effective than atropine in anti­ cannot be used as an indicator of systemic dotal action. poisoning or as a gauge for atropine dosage. If convulsions interfere with artificial Development of Specific Antidotes respiration and are not relieved by intrave­ Numerous investigators have sought to nous atropine, the patient may be given find agents that would interfere in the com­ trimethadione (Tridione), a barbiturate, or bination of the organic phosphorus com­ ether. Trimethadione may be given intrave­ pound with cholinesterase or hasten the nously or intramuscularly, in doses of 1 gm., destruction of the inactive phosphorylated repeated if necessary. Morphine should not enzyme complex. The deVelopment of specific be given. The action of succinyl choline antidotes of this type has been reviewed by ( Suxamethonium) increases the effect of the Davies and Green.33 The role of oximes in anticholinesterase agents, and thus the use of the treatment of anticholinesterase poisoning this relaxant is contraindicated (see "Chem­ has also been reviewed by Wills 145 and by ical and Physiologic Properties of Oximes"). Verhulst and Page.141 Results of treatment using transfusion Probably the usage of physostigmine with normal blood or even intravenous in­ (eserine) and neostigmine 26,70 represents fusion of purified cholinesterase have, in the earliest record of such attempts. It was general, been disappointing.14 It is doubtful found that, instead of an expected summa­ whether these materials provide any active tion or potentiation of effect occurring enzyme to important sites in the nervous tis­ between DFP and physostigmine or neostig­ sue. Their action in combining with any cir­ mine, prior administration of one of the lat­ culating poison is too little and too late to be ter agents protected rats against lethal doses of value in reversing the pathology associated of DFP. It was postulated that this antidotal with poisoning. effect was due to the formation between the It is important to understand that, while physostigmine or neostigmine and cholin­ atropine is effective as an antidote, it has no esterase of an unstable bond which served to effect on the fundamental biochemical lesion protect the active site on the enzyme from involved in poisoning by anticholinesterase attack by the irreversible inhibitor, DFP. compounds. Atropine merely serves to block The effectiveness of these particular agents Durham-Hayes 28 ARCHIVES OF ENVIRONMENTAL HEALTH

is strictly prophylactic, and they have no phorus moiety is split off and hydrolyzed. antidotal effect when given after the poison. The hydroxamic acid residue undergoes a An additive rather than an antagonistic ac­ further reaction to regenerate the active en­ tion was noted when physostigmine was zyme. The important thing from a practical given after DFP 97 or parathion.129 standpoint is that the hydroxamic acid has Somewhat later, Wilson 148,149 reported a greater affinity for the phosphorus moiety that choline and hydroxylamine were effective than does the enzyme. in reversing the combination between cholin­ Epstein and Freeman 46 have reported the esterase and certain organic Qhosphorus results of a study of the toxicity and prophy­ inhibitors. Wagner-Jauregg and his co-work­ lactic and therapeutic efficiency of a series ers 144 used certain metal salts and chelates of 15 hydroxamic acids in nerve-gas poison­ to reactivate DFP-inhibited enzyme. ing in mice. Other workers at the Army The most promising development, how­ Chemical Center 39 have made and tested 22 ever, is that associated with the hydroxamic oximes in this regard. O'Leary et al. 118 have acids and oximes.150 As pointed out above, tested a number of oximes both singly and it has been shown that the organic phos­ in various combinations. phorus compounds inactivate cholinesterase Of the hydroxamates and oximes tested by forming a firm bond with the enzyme. by various workers, the outstanding com­ This combination is commonly spoken of as pounds are 2-pyridine aldoxime methiodide "irreversible" in contrast to the combination ( 2- PAM iodide) and related salts. These of cholinesterase with physostigmine or neo­ compounds combine the features of low stigmine, which can easily be reversed by mammalian toxicity and good prophylactic dilution or dialysis. Actually, "irreversible" and therapeutic efficiency against organic must be regarded here as a relative term. In phosphorus poisoning. fact, TEPP-inactivated enzyme spontane­ Details regarding usage of oximes, and ously recovers some of its activity in vitro particularly of 2-PAM salts, in the treatment if allowed to stand in water for a sufficiently of anticholinesterase poisoning are consid­ long time. It is more difficult to reactivate ered in succeeding sections of this review. DFP-inhibited enzyme. 2-Pyridine aldoxime methyl methanesulfonate It would be expected that reagents (such (P2S), which is the methane sulfonate salt as esters or acids) capable of making a nu­ corresponding to 2-PAM, has recently been cleophilic attack on the phosphorus atom shown to be just as effective therapeutically of the inhibitor-enzyme complex could re­ as 2-P AM iodide 35 and to possess the ad­ generate the enzyme. Theory would further vantage of greater water solubility.34 The predict that presence within the reactivating methochloride salt of 2-pyridine aldoxime molecule of a cationic structure, such as the (2-P AM chloride) is more stable and more ammonium radical, would facilitate this re­ water soluble than 2- PAM iodide. The action by acting, as does the nitrogen atom methochloride salt is now commercially avail­ in acetylcholine, to properly position the able in the United States as an investigational molecule for its reaction with the enzyme. drug under the trade name Protopam. * The The hydroxamic acids and oximes fulfill lactate salt has been studied by O'Leary these requirements imposed by theory by et alY8 having both nucleophilic and cationic am­ In comparing the effects of these various monium groupings in the molecule. salts of 2-pyridine aldoxime, it is necessary The mechanism of action of oximes in re­ to take into account the variation in the generating inhibited cholinesterase is thought to consist of an initial direct combination * From Campbell Pharmaceuticals, Inc., 121 E. 24th St., New York 10. (The use of trade names between the organic phosphorus-inhibited is for identification purposes only and does not enzyme and the hydroxamic acid, followed constitute endorsement by the Public Health by a reaction in which the organic phos- Service.) Vol. S, July, 1962 ORGANIC PHOSPHORUS POISONING 29 amount of actual free base in the dosage ad­ known hepatotoxic agents (such as carbon ministered. For example, 1.0 gm. of 2-PAM tetrachloride) have a similar action. The chloride is approximately equal to 1.5 gm. of transitory rise in serum esterase apparently 2-PAM iodide with regard to content of the is a temporary consequence of the tissue active free-base, 2-pyridine aldoxime. damage occurring in the liver. Since the pro­ British workers 5,23,128 have proposed tective effect has been noted for a direct monoisonitroacetone (MIN A) and diacetyl­ inhibitor (TEPP) as well as for compounds monoxime (DAM) as being superior to which must undergo biotransformation in 2- PAM in combating organic phosphorus order to bet:ome toxic, a decreased activating poisoning. DAM is less toxic than 2-PAM.6 ability of the liver would not seem to be the These oximes reactivate sarin-inhibited cho­ mechanism of action. The most likely possi­ linesterase in vitro and are effective antidotes bilities appear to be an increased level of for sarin poisoning in rats. Robbiger and his phosphorylatable enzyme which competes co-workers 79·81 have tested a series of 18 with the true cholinesterase for the inhibitor, pyridinium oximes against TEPP and DFP or an increased level of hydrolyzing enzyme both in vitro and in vivo. They reported that which aids in the degradation of the anti­ certain monoximes and dioximes of poly­ cholinesterase. O'Brien 116 considers the lat­ methylenebispyridinium compounds were ter possibility to be more likely. from 15 to 52 times as potent as 2-PAM. Many of the organic phosphorus com­ Poziomek et al.llt) have also synthesized a pounds (including parathion, the other phos­ number of compounds in this series. The phorothioates, and some phosphoroamidates) outstanding antidotal compound from this become potent anticholinesterase agents only group is 1,1'-trimethylene-bis(4-formyl-pyri­ after bioactivation by the liver.116 It has dinium bromide) dioxime (TMB_4).15,52,711.81 proved possible to protect animals from com­ These other oximes have not been studied so pounds of this type by blocking the activating thoroughly as the salts of 2-PAM. enzymes present in the liver. Thus, Davison 36 Another type of specific antidote which was able to protect mice from poisoning by should be mentioned includes compounds octamethyl pyrophosphoramide (OM P A) which increase the hydrolytic activity of cho­ but not by parathion through prior adminis­ linesterase. Among the compounds which tration of the liver microsome inhibitor SKF have been shown in vitro to possess this sort 525A (,8-diethylaminoethyl diphenylpro­ of activity are tryptamine,50 certain anal­ pylacetate hydrochloride) . O'Brien and gesics,53 and other compounds.55 ,72,139 Most Davison 117 studied other liver microsome in­ of this work has been carried out with plasma hibitors, but found SKF 525A to be the best cholinesterase, although some studies using of 12 agents tested. They confirmed the fail­ the specific enzyme have been done. 11o,134,137 ure of SKF 525A to protect against para­ There is, at present, little or no indication thion but found that it antagonized Guthion that these agents would be of practical value insecticide poisoning. The lack of effective­ in the treatment of poisoning. ness of SKF 525A against parathion poison­ Ball and his co-workers 10 found that rats ing has not been satisfactorily explained. The which had been given a large but sublethal failure does not seem to represent a general dosage of aldrin were able to withstand ineffectiveness against phosphorothionates, amounts of parathion that would ordinarily since the LD50 of Guthion was increased. be lethal. This protective effect of aldrin was In connection with this effect on the enzyme accompanied by an increased plasma cholin­ system which activates the organic phos­ esterase level. Similar results have been noted phorus insecticides, it is interesting to note with other chlorinated hydrocarbon insecti­ that compounds are also known which inhibit cides, including chlordane, dieldrin, DDT, the enzyme systems that detoxify the organic heptachlor, and the a and y isomer (lindane) phosphorus compounds. Among the com­ of benzene hexachloride (BRe) .21},115 Other pounds producing this effect are certain of Durham-Hayes 30 ARCHIVES OF ENVIRONMENTAL HEALTH the organic phosphates themselves. Thus, phosphonate (EPN),1i6 while the maximum when given in combination, the resultant toxic synergistic effect (88 to 134 times.) noted has action of certain of the organic phosphorus been observed with malathion plus triortho­ compounds is greater than would be ex­ tolyl phosphate TOTP .109 The mechanism by pected on the basis of simple additive effect.1I6 which potentiation occurs has been elucidated This potentiation was first reported for mala­ and appears to involve the interference of thion plus ethyl-p-nitrophenyl thionobenzene one compound with the metabolism of the

Chemical Name Common Name Structural Formula

B;ydroxyl amine

Pyridine-2-alddxime 2-PAM or methiodide 2-PAM iodide

Pyridine-2-aldoxime 2-PAM chloride Same as above except methochloride or Protopam chlorine salt

Pyridine-2-aldoxime P2S methyl methanesulfonate

Diacetylmonoxime DAM

MOnoisonitrosoacetone MINA

I,ll-trimethylene bis(4-formyl-pyridinium THB-4 or bromide) dioxime TMB-4 dibromide

Chemical name, common name, and structural formula of oximes used as antidotes in poison­ ing by anticholinesterases. Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 31

Toxicity of Oximes to Experimental Animals

LD .. Compound Species Sex Route mg/kg Reference

2-P AM Iodide Mouse Mixed Intraperitoneal 136± 6 92 2-P AM Iodide Mouse Mixed Intraperitoneal 223±10 102 2-P AM iodide Mouse Unstated Intr" peritoneal 209±22 160 2-PAMiodide Meuse Unstated Subcutaneous 140±15 160 2-P AM iodide Mouse Unstated Intravenous 145± 8 118 2-PAM sulfonate Mouse Unstated In traven ous 118±13 118 2-PAM chloride Mouse Unstated Intravenous 115± 3 118 2-P AM chloride Rabbit Mixed Intravenous 95 118 TMB-4 dibromide Mouse Unstated Intravenous 53± 5 118 TMB-4 dlcbloride Mouse Unstated Intravenous 57± 1 118 TMB-4 dichloride Rabbit Mixed Intravenous 44 118

second.27.28.109 Seume and O'Brien 133 have doses are given, death usually occurs within reported that inhibition of carboxyesterase 10 to 20 minutes and is due to respiratory and carboxyamidase is important in potentia­ failure. Generalized clonic convulsions and tion of these compounds. gasping respiratory movements are seen. A potentiating effect between certain of the Generalized skeletal muscle tremors continue organic phosphorus insecticides and some for a few minutes after cessation of respira­ phenothiazine-derived tranquilizers has been tion. The similarity of this symptom picture found to occur in rats 64 and has been sus­ to that seen in organic phosphorus poisoning pected to occur in man.3 leads one to suspect that the mechanism of It has been noted that the signs and symp­ toxic action of 2-PAM may involve its ob­ toms of parathion poisoning were intensified served capacity to inhibit cholinesterase in and prolonged in a patient who was given excess dosages (see further details on succinylcholine for control of convulsions.12o page 34). In man, side-effects from the oximes Chemical and Physiologic 2-PAM iodide, 2-PAM chloride, and dia­ Properties of Oximes cetylmonoxime (DAM) have been minimal The chemical structure of 2-PAM iodide in normal subjects and practically nonexistent is shown in the Figure. The similarity of in people who were poisoned.68.69.87 Rapid the aliphatic portion of this molecule to intravenous injection of 2-PAM iodide has hydroxylamine is apparent. Pure 2-PAM produced transient mild weakness, diplopia, iodide is a yellow, crystalline solid which de­ blurred vision, dizziness, impairment of ac­ composes at 219 C. It is soluble in water up commodation, and occasionally headache, to about 5% and practically insoluble in ethyl nausea, and tachycardia.87 A few patients alcohol. Themethanesulfonate salt (P2S) is given 2-PAM iodide have complained of a soluble in water up to about 40%.34 The bitter taste that no doubt resulted from the chloride is soluble in water to the extent of iodine moiety of the molecule; 2-PAM iodide 1.0 gm. in less than 1.0 ml. has also produced an allergic rhinitis and a The toxicity to laboratory animals of vari­ feeling of fatigue in the jaws,11a ous oximes as determined by a number of Intravenous injection of DAM has caused different investigators is summarized in the a burning sensation at the site of injection Table. It can be seen that the estimate of the radiating up the vein, giddiness, drowsiness, intraperitoneal LDso of 2-PAM iodide to a sensation of warmth and tingling in the mice ranges from 136 to 223 mg. per kilo­ abdomen and chest, tachycardia, mild pos­ gram, and the intravenous LD50 ranges from tural hypotension,68 and occasionally bitter 44 to 145 mg. per kilogram for mice and taste, paresthesias and decreased position rabbits. The toxicity of the compound, while sense in the extremities, decreased sweating, important, is not especially great. When lethal transient loss of consciousness, clonic move- Durham-Hayes 32 ARCHIVES OF ENVIRONMENTAL HEALTH ments of the head, and decreased amplitude reactivation of inhibited enzyme was respon­ of the electroencephalogram and of the T­ sible for the effect of DAM in this instance. wave segment of the electrocardiogram.87 Kewitz 90 has shown that 2-PAM iodide Many of the oximes liberate cyanide in the reactivates the esterase activity of diaphragm body and also on long standing in vitro.8,11l in the living animal poisoned with paraoxon When there is doubt concerning the integrity or DFP, but not OMPA. These results paral­ of a 2-PAM preparation, particularly solu­ lel those obtained in vitro with the same com­ tions of old or uncertain age, a simple test pounds and afford good evidence that the for free cyanide should be carried out. antidotal properties of 2-PAM depend upon lt should be noted that 2- PAM salts have reactivation of inhibited cholinesterase. at least 3 actions which may be of importance Cohen and Wiersinga 215 reported that both in their effect on animals poisoned by organic MINA and 2-PAM iodide rege'1erated dia­ phosphorus compounds. These actions are: phragm cholinesterase in vivo in sarin­ 1. Reactivation of inhibited cholinesterase. poisoned rats. Inhibited brain cholinesterase 2. Reaction with and inactivation of the organic was reactivated by MINA only. phosphorus molecule. 3. Inhibition of cholinesterase, especially in excess Some workers 7,78 have not been entirely dosage. satisfied with this explanation for the anti­ The reactivation of inhibited cholinesterase dotal efficacy of 2-PAM, and, in support of is the dominant effect of 2-PAM in poisoned their view, point out that the therapeutic animals. In vitro, 2-PAM is a very powerful efficacy and in vitro cholinesterase reacti­ reactivator. At a concentration of 1O-5M., vating power of the oximes do not correlate 2-PAM iodide reactivates as much as 80% very closely. One would do well to remember, of alkyl phosphate-inhibited enzyme within however, that the other 2 actions of oximes 1 minute.154,31,23 The diisopropyl phospho­ (numbers 2 and 3 above) must also be con­ rylated enzyme is reactivated more slowly and sidered and may explain the observed lack less completely than the diethyl substituted of correlation. cholinesterase.77 In a comparative in vitro In contrast to the marked rise of enzyme study of 2-PAM iodide, DAM, and mono­ activity in blood and muscle following the isonitroacetone (MIN A), Cohen and Wier­ administration of 2-PAM, little or no effect singa 24 found that 2-PAM iodide was the has been noted on inhibited brain cholinester­ most efficient reactivator, followed closely by ase.78 ,128,1l0,91,25 This failure of 2-PAM to MINA. The reactivation by DAM was slow reactivate brain cholinesterase has usually when compared with those of the 2 other been ascribed to a supposed inability of the oximes. In a later paper, Cohen and Wier­ oxime to pass the blood-brain barrier. In singa 25 theorized that the antidotal efficacy earlier work, Koelle and Steiner 96 had shown of DAM was primarily due to its ability to that quaternary nitrogen compounds pene­ inactivate the organic phosphorus molecule trate the blood-brain barrier with difficulty. rather than its capacity to regenerate inhibited However, even when administered intracis­ cholinesterase. Rajapurkar and Panjwani 124 ternally, P2S had no effect on the central suggested that DAM had an antiacetylcholine actions of sarin. Holmstedt 84 considered that effect, like that of atropine. Their hypothesis the observed failure of 2-PAM iodide to was based on study of ciliary movement in restore respiration depressed by anticholin­ the frog esophagus. This preparation has esterase was due to its inability to penetrate been shown to contain the acetylcholine­ the blood-brain barrier. Jager et a1. 88 found cholinesterase-choline acetylase system, but low concentrations of 2-P AM iodide in the no nervous tissue. DAM produced slowing brain of 2 rabbits infused with this antidote. of the ciliary movement similar to that pro­ Wilson 152 has attempted to overcome this duced by atropine or curare. The action was difficulty by using the fat-soluble dodecanoic the same in eserinized or normal cilia. Thus, acid analogue of 2-PAM with only partial apparently neither a central mechanism nor a success. In contrast to these results, Rosen- Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 33

berg 126 has noted in vivo reactivation of Porath 44 have noted synergIsm between brain cholinesterase by 2-PAM iodide after 2-P AM and DAM. paraoxon poisoning in the rabbit. Rosenberg At any given dosage with any given inhibi­ considered that the differences between his tor and reactivator, the extent of reactivation results and those of others cited above might of cholinesterase activity that occurs depends be due to species variation or to the use of upon how long the inhibitor and enzyme have different extraction procedures. Differences been left in contact.76 Hobbiger theorized that in dosage levels of 2-PAM may also have the phosphorylation of cholinesterase led in­ been a factor, since Rosenberg gave very high itially to an unstable phosphorylated enzyme dosages (up to 250 mg. per kilogram). which gradually changed to an irreversibly The marked effectiveness of 2-PAM phosphorylated enzyme. This phenomenon iodide, 2-PAM chloride, and TMB-4 in has been termed "aging" by O'Brien 116 and poisoning by Phospho line Iodide in mice is has been shown to occur in vivo 78 as well as considered to be related to the fact that phos­ in vitro.151 ,32 Aging occurs rather slowly with pholine, in contrast to other organic phos­ methylphosphorylated cholinesterase, but phorus cholinesterase inhibitors, contains a more rapidly with diethyl- or diisopropyl­ quaternary nitrogen atom, and thus, like the substituted enzyme.32 These results indicate quaternary oximes, fails to pass the blood­ that the oximes might be less effective in brain barrier.911 regenerating- cholinesterase inhibited during TMB-4 did not reactivate brain cholin­ repeated exposure than that inactivated after esterase activity in rats poisoned with DFP a single exposure. or sarin.51 The use in vitro of a reactivator in the Jager et al. 88 were not able to demonstrate routine cholinesterase test has been proposed 2-PAM iodide in the cerebrospinal fluid in a to allow determination of both inhibited and man who received 44 mg. per kilogram of normal enzyme levels in a single blood sample this oxime intravenously. However, rapid re­ from a patient in whom poisoning is sus­ turns to consciousness following administra­ pected.3 The occurrence of aging would seem tion of 2-P AM iodide have been noted in to make achievement of this objective un­ patients poisoned with parathion. 811 ,49,121 This likely in connection with repeated exposure; clearing of consciousness would seem to be but it should be possible, by use of a similar an indication that the drug has access to the technique, to differentiate between an inhibi­ brain in man. The practical clinical result tion of cholinesterase due to a recent, acute may be further evidence for species variation exposure and a depression due to a previous in the action of 2-PAM. or repeated exposure. In contrast to the peripherally-acting qua­ Direct reaction between 2-PAM and the ternary oximes (2-PAM and TMB-4), the organic phosphorus molecule has been shown nonquaternary oximes have a predominantly to occur.143 ,T7 The importance of this reaction central action.146,19 DAM has been shown in either the prevention of dermal absorption to penetrate the blood-brain barrier and effect or local effects of anticholinesterase com­ some reactivation of brain cholinesterase.88,43 pounds or both has been discussed by However, DAM in large doses has produced Summerson.159 Kewitz, Wilson, and Nach­ coma in man.87 mansohn 93 have, however, pointed out that O'Leary et al. 118 have reported that atro­ it is unlikely that the direct reaction is an pine and a combination of a mono quaternary important factor in the antidotal action on and a bisquaternary oxime were superior to systemic effects in vivo, since in vitro experi­ atropine with either single type of oxime in ments have shown that this direct reaction dogs and rabbits poisoned with sarin or is very slow at concentrations obtainable tabun. AI: 1 mixture of 2-P AM chloride and under physiological conditions. These authors TMB-4 dichloride was the most effective note that even with a 1O-3M. concentration combination tested. Edery and Schatzberg- of 2-PAM iodide at 25 C, pH 7.8, only about Durham-Hayes 34 ARCHIVES OF ENVIRONMENTAL HEALTH

1 % of diethyl p-nitrophenyl phosphate Wagley.16 These workers reported that (Paraoxon, 1O-4 M.) reacts per hour. Cohen 2- PAM iodide in high concentration in vitro and Wiersinga 25 found that both DAM and had a dual effect on motor end-plate cholin­ MINA detoxified sarin during in vitro incu­ esterase previously inactivated by TEPP. bation. No detoxication of sarin by 2-PAM The 2-PAM iodide reactivated the enzyme iodide occurred. These authors suggested and, if allowed to remain in contact with the that DAM acts mainly by virtue of direct preparation, inhibited the reactivated enzyme. reaction with the toxicant, that 2-PAM acts It is important to note that in poisoned primarily by reactivating inhibited enzyme, people given therapeutic doses, the inhibition and that MINA shows both types of activity. of cholinesterase by 2-PAM is trivial, while At sufficiently high dosages, 2-PAM iodide the release of enzyme inhibited by the organic is capable of inhibiting both serum and eryth­ phosphorus compound is highly significant. rocyte cholinesterase in vitro.8'2.T7.68 Although Kewitz et al.lI3 have carried out experi­ the antidotal dosages which have generally ments which show that 2-PAM does not have been used are below the toxic level, there an atropine-like action. In studies on the would seem to be, on the basis of studies blood pressure of eviscerated cats, the effect reported by Loomis,102 a definite possibility of acetylcholine was not modified by 2-PAM of lessened antidotal effect if greater than iodide, even when large doses were used; the optimal dose of 2-PAM were given. This this effect was completely abolished by a small author noted that dogs given an intravenous dose of atropine, however. After 100 mg. dose of 60/Lg. of sarin per kilogram required per kilogram of 2-PAM iodide, these authors more than 240 minutes to recover their nor­ reported a rise in blood pressure from 120 mal response to injected acetylcholine. Fol­ to 160 mm. Hg which lasted 15 to 20 minutes lowing intravenous administration of 10, 25, and was abolished by atropine. This effect or 250 mg. per kilogram of 2-PAM iodide from the very large dose of 2-PAM iodide to normal dogs, <2, 3, and > 120 minutes, was not further studied. Possibly, it was a respectively, were required for return of the reflection of the cholinesterase inhibitory normal acetylcholine response. The same effect of 2-PAM. dosage levels of 2-P AM iodide when given Both 2-PAM iodide and DAM, when in­ to sarin-poisoned dogs, produced return to jected intravenously in large doses, have a normal acetylcholine response after 40 to 45, direct depressant action on the respiratory 80 to 100, and > 120 minutes, respectively. center.156 These results indicate that 2-PAM iodide The duration of action of a single dose of is a cholinesterase inhibitor, that 10 mg. per 2-PAM has been studied by Kewitz et al.lI3 kilogram was the optimum antidotal dosage Following intraperitoneal dosage, 2-PAM under the condition of the test and that larger iodide reached its maximum effect in rats doses were less effective. within 30 minutes and had declined to about Woodard 158 gave 50 mg. per kilogram of 50% of maximum effectiveness at the end 2-P AM iodide to cattle intraperitoneally and of the first hour. A further decline in activity intravenously. This dosage produced some took place during the second hour, but even restlessness and mild abdominal distress, but at the end of 2 hours, some protective effect the signs were mild and of short duration. was still evident. Following intravenous One sheep given 25 mg. per kilogram of dosing, 2-PAM iodide appears to be well 2- PAM iodide intravenously showed the dispersed in all body tissues with the excep­ same signs as the cattle, plus an increased tion of the brain.88 These same authors found respiratory rate and excessive salivation. that 2- PAM iodide was rapidly excreted in No change in erythrocyte cholinesterase level man following intravenous dosage. The half­ was observed in any of these animals. life was 0.9 hours. Excretion was primarily The cholinesterase inhibitory activity of by the kidneys. In nephrectomized dogs and 2-PAM has also been noted by Bergner and rats and in a patient with chronic nephritis Vol. S, July, 1962 ORGANIC PHOSPHORUS POISONING 35 and azotemia, excretion was retarded. In that the reversal of neuromuscular block is vitro, 2-PAM iodide was metabolized aero­ due entirely to a reactivation of inhibited bically by rat liver slices. cholinesterase in the muscle. Wislicki 156 P2S is also rapidly excreted in man follow­ noted that DAM reduced direct and indirect ing intravenous dosing.136 Absorption of P2S muscular excitability to a marked extent, after intramuscular or oral administration while with 2- PAM iodide these effects were was not satisfactory. slight and were obtained only after intra­ DAM is excreted somewhat more slowly arterial administration. Application of 2- in man than is 2-PAM iodide.88 The half-life PAM antagonizes the block caused by the for the former compound is 7.2 hours. Rela­ competitive type of blocking agent, such as tively little of the DAM could be recovered curare, and it intensifies the effect of suxame­ from the urine. Apparently, the liver is of thonium. DAM has no definitive influence major importance in the metabolism of on the former but prolongs the action of the DAM.311,88 latter. Neostigmine, unlike atropine, antago­ Loomis 103 has tried 2-P AM in the treat­ nizes the depression of muscle excitability by ment of local ocular effects of TEPP and DAM but has no marked effect on the action sarin in rabbits. He found that 2-PAM of 2-PAM. iodide applied locally was very effective in Longo et al.1°1 have reported that the reversing miosis induced by organic phos­ threshold level of sarin necessary to produce phorus compounds. The reversal was brought a "grand mal" electroencephalographic pat­ about by 2- PAM iodide in 2 to 3 hours; tern was increased about threefold by 2-PAM whereas, if allowed to remit spontaneously, it iodide. However, 2-P AM iodide had no effect required from 24 to 48 hours or even longer. on the early phase of desynchronization of The most effective dosage form was a petro­ the electroencephalogram. latum-based ointment, containing 0.1 % of 2-PAM iodide. In contrast to Loomis' results, Antidotal Efficacy of Oximes in Poisoned Kewitz et al.1l3 reported that local application Experimental Animals of 2-PAM iodide had no effect on a rabbit's pupil constricted by placing diethyl p-nitro­ There are now in the published literature phenyl phosphate in the eye. However, intra­ numerous reports giving results of the usage venous injection of 50 mg. per kilogram of of 2-PAM salts and other oximes in labora­ 2- PAM iodide brought the pupil back to tory animals poisoned with various organic normal size and restored reactivity to light phosphorus compounds. The compounds within 5 minutes. The formulation in which studied have included demeton,130 DFP,1l3,20, 2-PAM iodide was used for local application 78,52 Diazinon,131 dime fox, 131 dimethoate,131 was not stated. It may be that the lack of endothion,54 Ethyl Guthion,130 Guthion,l30 effect was due to use of a water solution of methyl demeton,54 methyl parathion,131 mor­ 2-PAM iodide rather than an oil-based prep­ phothion,130 paraoxon,1l2.93,17,78 parathion,17, aration. 155,54,131 phencapton,131 Phosdrin,130 phos­ Application of 2- PAM iodide 82,147 and phamidon,l3o,86.108 Phospholine Iodide,99 sa­ MINA 82 relieves the neuromuscular block rin,t OMPA,93 tabun, 20.155.52 TEPP,78.155. 130 caused by anticholinesterases. Grob and 35.52 and phorate. Most workers have Johns 68 reported that DAM reversed the found that the combination of oxime and local neuromuscular block produced by anti­ atropine is superior to either antidote used cholinesterases in man, but Edery 43 did not alone. However, Sanderson 130 did not note note this effect in the cat or the rat. In this any increased benefit of an oxime (2-PAM connection, it would be of interest to study iodide or P2S) plus atropine in comparison the effect of these oximes on the paralysis with atropine alone in rats given oral doses caused by certain organophosphorus com­ of 10 organic phosphorus and carbamate in- pounds. Holmes and Robins 82 have stated t References 102, 6, 147, 155, 35, 145, and 52. Durham-Hayes 36 ARCHIVES OF ENVIRONMENTAL HEALTH

secticides. With oral Guthion, Ethyl Guthion, shown that 2-PAM iodide and DAM reverse demeton, and morphothion, 2- PAM iodide the physiological effects of neostigmine apparently reduced the beneficial effect of (which is a substituted carbamate.) and sev­ atropine. This author did note potentiation eral of its derivatives.68 between atropine and oxime in some instances when the poison was given intraperitoneally. Application of 2-PAM in Sanderson and Edson 131 concluded that the Poisoning in Man relative effectiveness of oxime therapy with The oxime 2-PAM has now been used in different organic phosphorus insecticides de­ the treatment of poisoning in man in a num­ pends on the proportion of reversible cho­ ber of instances. linesterase inhibition present, as predicted on Namba and Hiraki 114 have reported a the basis of the structure and duration of series of 5 cases. All of these cases were action of the anticholinesterase compound. classified by the authors as serious-indicat­ The efficacy of 2-PAM in the treatment of ing a potentially fatal outcome-if untreated. poisoning varies from compound to com­ However, one of those patients was already pound, but it has shown some effectiveness asymptomatic at the time he received 2-PAM in the case of all the materials listed above iodide. A second patient who had previously with the exception of dimefox, dimethoate, received 10 mg. of atropine showed no clini­ and OMPA. In this connection, it is interest­ cal improvement immediately after receiving ing to note that Tammelin and Enander 138 100 mg. of 2-PAM iodide intravenously. He reported synthesis of an organic phosphorus did, however, improve about 3 hours later compound (cholinyl methylphosphonofluori­ (6 hours after onset of symptoms). A third date) which caused an inhibition of cholin­ case was given ten 100-mg. intravenous doses esterase that could not be reversed in vitro of 2-P AM iodide during a period of 3.5 by 2-PAM iodide. hours. By the end of this time, all symptoms Woodard 158 has reported results of stud­ had disappeared. A fourth patient became ies with 2- PAM iodide in cattle and sheep symptom-free after doses of 500 and 400 poisoned with organic phosphorus illsecti­ mg. of 2-PAM iodide, separated by 10 min­ cides. N either atropine nor 2-P AM iodide utes. The fifth case received 1 gm. of 2- alone was a satisfactory antidote in these P AM iodide intravenously, which the authors animals. A combination of 2-PAM iodide considered to represent the ideal treatment. and atropine gave good results on cattle Within 21 minutes, all the symptoms in this poisoned with parathion or Diazinon, but not fifth case, including muscle fasciculations, on cattle poisoned with malathion or on sheep had disappeared. poisoned with parathion. In 3 of the 5 cases cited above, the erythro­ It appears likely that different oximes have cyte cholinesterase level returned to normal some specificity not only for different or­ in 10 minutes, 40 minutes, and 3.5 hours, ganic phosphorus compounds but also for respectively. In the fourth case the recovery different species. of the red-cell enzyme was signific;mtly more The effectiveness of oximes as antidotes rapid than that of the untreated control. In has also been tested in poisoning by certain the fifth case, it is not clear from the data other cholinesterase inhibitors which are not presented that the red-cell enzyme level was organic phosphorus compounds. The use of ever significantly depressed. No immediate 2-P AM iodide has been reported to be in­ effect of 2-PAM iodide on plasma cholin­ effective, if not detrimental, in the treatment esterase was evident, but in all treated cases of poisoning by the carbamate insecticide studied, this enzyme returned to a normal Sevin in rats and dogS.22,180 On the other level more rapidly than did the untreated con­ hand, poisoning in the rat by the carbamate trol. insecticides Isolan and Dimetilan was bene­ It should be especially noted that the re­ fited by 2- PAM iodide.130 It has also been covery in 4 out of 5 of these human cases was Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 37 after 2-PAM iodide alone. Only 1 of the little or no effect on plasma enzyme (0.04 patients received a combination of 2-P AM ~ pH per hour). iodide and atropine. The work with experi­ Quinby and Clappison 121 used 2-P AM mental animals cited above would lead one iodide in the treatment of a 2-year-old child to expect that a combination of both drugs who ate dirt contaminated with parathion. would be more effective than either alone. The child was given an intravenous dose of In a later paper, Namba 112 reported the 250 mg. of 2-PAM iodide following repeated results of the use of 2-PAM iodide in an doses of atropine. The critically ill, uncon­ additional 26 cases of accidental parathion scious child returned to an almost normal state poisoning and in 2 cases of attempted suicide in less than 20 minutes after the oxime dosage by ingestion of parathion. The accidental was given. The levels of both plasma and poisonings were treated with 1 to 2 gm. of erythrocyte cholinesterase were near 0 before 2-PAM iodide intravenously. Marked im­ 2-PAM, but 20 minutes after its administra­ provement was noted within 30 minutes. tion, the erythrocyte cholinesterase level had Pallor was the only symptom remaining in returned to within the range of normal. The 5 cases, miosis in 3 cases, and difficulty of reactivation of plasma enzyme level was much speech and tachypnea in 2 cases. These re­ slower, the normal level being reached be­ maining symptoms had cleared within 1 hour tween the third and nineteenth days. p-Nitro­ after treatment. Complete recovery of con­ phenol was excreted in the urine quite rapidly, sciousness occurred in 5 cases. Symptoms clearing in about 30 hours from ingestion. such as nausea, headache, dizziness, and Schvartsman and his colleagues 132 treated numbness of extremities did not respond as a child who had ingested a commercial solu­ well to 2-PAM as did the others just men­ tion of parathion. The treatment included milk, atropine, stropanthin, and 300 mg. of tioned. Some of these effects persisted for as 2-PAM sulfonate. The child regained con­ long as 1 week. To be effective in cases of sciousness and began to improve after treat­ ingestion of parathion, it was necessary to ment; he was discharged from the hospital give very large doses of 2-PAM. Continu­ after 3 days. ous intravenous infusion of 2-PAM at the Karlog et al. 89 have reported the treatment rate of 0.5 gm. per hour is preferred by Dr. with atropine and 2-PAM iodide of a patient N amba. One patient received a total dose who attempted suicide by taking an estimated of 40.5 gm. of 2-PAM iodide, recovering 1.75 gm. of parathion by mouth. This patient without apparent ill effect. Namba 112 men­ was given very large doses of atropine tioned exploratory study of the use of 2- beginning soon after poisoning. His respira­ PAM for the prophylaxis of parathion tion ceased, and he was given artificial respi­ poisoning. ration for 5 hours after poisoning. He was Funckes 62 has reported the successful not given any 2- PAM until 2.5 days after treatment with 2-P AM iodide and atropine poisoning. During the next 12 hours he was of a severe case of occupational parathion given 3.5 gm. of the antidote. Each dose of poisoning. This patient was given 1 gm. of 2-P AM iodide produced transitory rises in 2-P AM iodide intravenously about 1 hour plasma and erythrocyte cholinesterase ac­ after illness began, and he improved dramati­ tivity which persisted for only a few hours, cally within 10 minutes. Although blood but the patient eventually recovered. cholinesterase levels prior to administration Rosen 1'25 treated with 2-PAM iodide a of 2-PAM iodide were not determined, the young man who was poisoned by accidentally enzyme activities after the drug was given spilling a gallon bottle of parathion concen­ indicated reactivation of erythrocyte cholin­ trate on his hands. This patient was given esterase (0.32 ~ pH per hour) as measured adequate doses of atropine during the first 18 by the method of Miche1 107 and expressed hours after poisoning, and by the end of this in terms of change of pH per hour; there was time he was symptom-free except for per- Durham-Hayes 38 ARCHIVES OF ENVIRONMENTAL HEALTH

sisting muscular weakness. After 2-P AM A formulating plant worker studied by was administered, prompt improvement in Quinby and Congdon 122 became poisoned muscle strength was noted. while working with parathion. He had a very One of the most severe poisoning cases low blood cholinesterase level (plasma 0.10 treated with 2-PAM is that reported by and erythrocytes 0.08 A pH per hour) during Imo.85 A young girl drank parathion with his acute illness and was given atropine ther­ suicidal intent. She was found unconscious, apy. His gastrointestinal complaints, par­ in convulsions, foaming at the mouth, and ticularly anorexia and nausea, as well as unreactive even to the strongest stimulus. weakness, headache, and malaise, persisted. She had almost no pulse and was cy­ He continued to work in the plant, although anotic and areflectic. Atropine, artificial presumably he was removed from direct con­ respiration, Stereofundin, and nikethamide tact with insecticides. However, his urinary (Coramine) were given, and spontaneous p-nitrophenol excretion indicated continued respiration was restored. About 9 hours later, exposure to parathion. Because of these con­ 500 mg. of 2-PAM iodide was given. Within tinuing symptoms, and in an attempt to raise 1 hour, the patient regained color, became his blood cholinesterase level sufficiently to completely conscious, and her pupillary re­ permit his safe return to his regular work, flexes returned to normal. Further recovery this man was given 1 gm. of 2-PAM chloride was uneventful. 6 days after his acute illness. The antidote Other instances of parathion poisoning had little or no effect on his blood cholinester­ treated with 2- PAM include a series of 10 ase level, but he felt much better the next cases (of which 6 were attempted suicide) mormng. reported by Erdmann.47 Three of these pa­ It is apparent from brief case reports that tients recovered, 3 died, and in 4 cases the the use of 2-PAM in combination with outcome is not indicated. atropine is considered effective and is routine in the treatment of poisoning by organic phos­ Erdmann and Latki 48 have used 2-PAM phorus insecticides in Israel.2 iodide in the treatment of a case of poisoning from inhalation of DFP. The administration Suggestions for Treatment of atropine and 2-PAM iodide (2 doses of 500 mg. each, orally, 2 and 5 hours after ex­ The following suggestions are provided as posure) produced prompt remission of a guide to the physician who may be called symptoms with the exception of miosis, which upon to treat persons poisoned by anti­ persisted for 8 to 10 days and led to a severe cholinesterase compounds: I. In very severe cases, the order of treatment conjunctivitis. Some increase in erythrocyte should be as follows: cholinesterase activity was noted after 2- (1) ARTIFICIAL RESPIRATION, pref­ PAM, but the enzyme level did not return to erably by mechanical means. normal until about 30 days later. (2) ATROPINE, 2 to 4 mg. (1/30 to 1/15 grain) intravenously as soon as cyanosis In 2 cases of moderately severe 2-carbo­ is overcome. Repeat at 5- to lO-minute in­ methoxy-l-methyl-vinyldimethyl phosphate tervals until signs of atropinization ap­ (Phosdrin) poisoning, Funckes 63 noted a pear (dry, flushed skin and tachycardia less dramatic clinical response to 2-P AM as high as 140 per minute). (3) 2-PAM, 1 gm. slowly, intravenously. iodide than in the case of parathion poisoning. (4) DECONTAMINATION of the skin, Both of the 2-P AM -treated Phosdrin cases stomach, and eyes as indicated. continued to show symptoms of poisoning for (5) SYMPTOMATIC TREATMENT. several hours after receiving the antidote. II. In the more usual case, proceed as follows: However, the erythrocyte cholinesterase level (1) ATROPINE, 1 to 2 mg. (1/60 to 1/30 If was significantly increased, and the plasma grain), if symptoms appear. excessive secretions occur, keep the patient fully enzyme was regenerated to a lesser degree atropinized. Give atropine sulfate every after 2-P AM therapy. hour up to 25 to 50 mg. in a day. Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 39

(2) DECONTAMINATION of the skin, Until 2-PAM is freely available for pre­ stomach, and eyes as indicated. scription it is recommended that the limited (3) 2-PAM, 1 gm. slowly, intravenously if supply not be drawn upon in cases of mild the patient fails to respond satisfactorily to atropine. poisoning or in cases that show a completely (4) SYMPTOMATIC TREATMENT. satisfactory response to atropine. It will be noted that this recommended Consideration should be given to local ap­ dosage of atropine is greater than that con­ plication of 2-PAM to the skin to reduce ventionally employed for other purposes but dermal absorption in exposed persons, and is within safe limits. People poisoned by to the eyes to reverse organic-phosphorus-in.­ anticholinesterase organic phosphorus com­ duced miosis. The use of 2-PAM for the pounds have an increased tolerance for atro­ prevention rather than the treatment of sys­ pine. For additional discussion of atropine temic poisoning has been proposed. These usage, see "Use of Atropine and Other Non­ procedures seem to be safe on the basis of specific Antidotes," above. limited studies with experimental animals, Although different oximes offer somewhat although their effectiveness has not been different therapeutic possibilities, 2-PAM ap­ proved. These procedures are strictly ex­ pears to be the most generally useful oxime ploratory, while the value of 2-PAM for treatment of systemic poisoning, especially now available. There appears to be no es­ by parathion, is established. sential difference in the effects of the differ­ ent salts of 2-PAM, and 2-PAM chloride N ever give morphine, theophylline, or theophylline-ethylene-diamine (aminophyl­ does have the advantage of greater solubility line) to a patient poisoned with an anticholin­ and lack of iodine taste as compared to 2- esterase agent. Do not give atropine to a PAM iodide, which used to be more easily available. A dosage of 10 to 20 mg. per kilo­ cyanotic patient; give artificial respiration first, and then give atropine. Large amounts gram has proved a safe but generally effective level. As a round figure, 1 gm. should be an of intravenous fluids are generally contra­ indicated because of excessive fluid in the average adult dose. Intravenous administra­ respiratory tract. Tranquilizers should be tion is recommended to obtain rapidity of used with great caution; they are seldom action. Since 2-PAM is excreted rapidly, indicated at all. Succinyl choline should not repeated doses may be necessary, particularly be given. in cases involving parathion or other com­ If pulmonary secretions have accumulated pounds that must undergo bioactivation be­ before atropine has become effective they fore becoming toxic. It is important to note, should be removed by suction and a catheter. however, that the only known signs or symp­ If the stomach is distended, empty it with a toms of overdosage with 2-PAM are identical Levine tube. to the manifestations of poisoning with anti­ If the patient has not yet shown symptoms cholinesterases. 2-PAM should be adminis­ or they have been allayed by treatment, he tered in conjunction with adequate doses of must be completely and quickly decontami­ atropine. Other supportive treatment, includ­ nated. Remove the patient's clothing and, ing particularly artificial respiration, should with due regard for his condition at the also be carried out as required. moment, bathe him thoroughly. Remove any The value of 2-PAM is most thoroughly visible insecticide gently with a generous established in connection with the treatment amount of soap and water or other detergent of poisoning by parathion. When used in if available. Avoid abrasion. When the skin cases of poisoning by other organic phos­ appears clear, bathe or swab with ethyl al­ phorus insecticides, it should be with the cohol. Parathion and many of the other or­ awareness that it may be somewhat less ef­ ganic phosphorus insecticides are very much fective. In fact, 2-PAM appears to be in­ more soluble in alcohol than in water, and effective in treating poisoning due to OMPA. significant amounts can be washed from skin Durham-Hayes 40 ARCHIVES OF ENVIRONMENTAL HEALTH

that has been scrubbed several times with The acute emergency lasts 24 to 48 hours, soap and water. and the patient must be watched continuously I f there is any suspicion that the poison during that time. Favorable response to one has been ingested or inhaled and if the patient or more doses of atropine does not guarantee is still responsive, induce vomiting, give some against sudden and fatal relapse. Medication neutral material such as milk or water, and must be continued during the entire emer­ induce vomiting again. The reason for men­ gency. Any person who is ill enough to re­ tioning inhaled material is, of course, that a ceive a single dose of atropine should remain large portion of it is deposited in the upper under medical observation for 24 hours, be­ respiratory tract and subsequently carried to cause the atropine may produce only a tempo­ the pharynx and swallowed. Nausea may be rary relief of symptoms in what may prove anticipated on the basis of the systemic action to be a serious case of poisoning. Atropine of these compounds, but if vomiting is not should never be administered for preventive profuse, gastric lavage may be used. Experi­ purposes to persons who have not become ments have indicated that vomiting induced sick. immediately or even 1.5 hr. after ingestion is Miosis and headache may persist after re­ more effective than gastric lavage in removing covery from poisoning by organic phosphorus pOlson. insecticides is otherwise largely complete. In some cases, the systemic administration of It must be kept in mind hOW little parathion is necessary to produce poisoning by the oral atropine is followed by partial or temporary route. Repeated dosage at the rate of 7.2 dilatation of the pupils. Miosis responds mg. per man per day led to moderate reduc­ more dependably to 2-PAM. If further tion of blood cholinesterase activity.44a A systemic treatment is not necessary, the mio­ dose of 25 to 50 mg. was fatal to a child,132a sis and associated headache will respond to and a dose of 120 mg. was fatal to an adult.17a the instillation of 0.5% to 1% atropine solu­ tion or 0.5% atropine ointment into the eyes. Atropine does not protect against muscu­ Following exposure heavy enough to pro­ lar weakness. The usual mechanism of death duce symptoms, further organic phosphorus appears to be respiratory failure. The use insecticide exposure of any sort should be of an oxygen tent or even the use of oxygen avoided. The patient may remain susceptible under slight positive pressure is advisable to relatively small exposures to the same or and should be started early. Watch the patient any other organic phosphorus compound constantly, since the need of artificial respira­ until regeneration of cholinesterase is nearly tion may appear suddenly. Equipment for complete. oxygen therapy and for artificial respiration should be placed at the patient's bedside in Prevention of Poisoning readiness while the patient is on his way to The most important single factor in the the hospital. Cyanosis should be prevented prevention of poisoning is a knowledge of by the most suitable means, since continued the hazards involved in handling the various anoxia aggravates the depression of the anticholinesterase compounds. It is essential respiratory center caused by the poison direct­ that the facts about the toxicity of these ma­ ly. Complete recovery may occur even after terials be learned through research and then many hours of artificial respiration have been that these facts be made known to all con­ necessary. cerned, including the formulating plant If there is any reason to think that the worker, the commercial sprayman, the eyes may have been contaminated, irrigate farmer, the householder (who may purchase them with isotonic saline solution or water. these insecticides for use in his house or The absorption of some of the organic phos­ garden and, if not adequately warned, may phorus insecticides by the eye is remarkably leave the toxic materials accessible to children rapid. or other irresponsible persons), and the

Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 41 physician who may be called upon to treat based on blocking the action of excess acetyl­ pOlson mg. choline, but it has no effect on the basic In persons occupationally exposed, poison­ biochemical pathology involved in anticholin­ ing can best be prevented by constant, esterase poisoning. With regard to symptoms, thoughtful care and by use, where indicated, atropine is effective in treating those effects of safety devices such as protective clothing, referable to the central and muscarinic action respirators, masks, air-conditioned cabs, or of acetylcholine but has no effect on the nico­ special factory ventilation. tinic action. More recently a series of antidotes has been Prevention can also be approached by ob­ developed that are able to reverse the com­ serving trends in serial blood cholinesterase bination between the cholinf'sterase molecule determinations on persons constantly ex­ and the inhibitor. These compounds are posed. The interpretation of individual oximes and include salts of, for example, 2- values in asymptomatic persons is difficult. PAM (2-pyridine aldoxime methiodide) , It is clear, however, that a single very low DAM (diacetylmonoxime), MINA (mono­ enzyme value for one worker or a low isonitrosoacetone) and TMB-4 (I,l'-trimeth­ average value for a group of exposed work­ ylene bis ( 4-formyl-pyridinium bromide) ers is an indication of the need for improved dioxime) . Since the oximes and atropine personal care or better mechanical protection have different sites of action in the mam­ or both. In a similar way, prevention of malian body, it is preferable to use these 2 poisoning may be helped by proper evalua­ tion of the amount of urinary excretion of agents in combination and thus take advan­ biotransformation products. tage of the antidotal effects at both points. The most widely used of the oximes in Direct methods are also available to meas­ treating poisoning is 2-PAM. This com­ ure the exposure which spray operators have pound has at least 3 actions that may be of to pesticides during their usual conditions of importance in the treatment of poisoning by work.42 an organic phosphorus compound. These Severe poisoning may at times be pre­ actions are: ( I) reactivation of inhibited vented by the immediate recognition and cor­ cholinesterase, (2) reaction with and inac­ rection of contamination. Prompt, effective tivation of the organic phosphorus molecule, medical treatment may prevent a mild poison­ and (3) inhibition of cholinesterase. Atro­ ing case from developing into a serious one. pine has none of these actions. The dominant effect of therapeutic doses of 2-P AM in Comment and Summary poisoned animals is reactivation of inhibited Poisoning due to organic phosphorus com­ cholinesterase. Application of 2-P AM re­ pounds may be encountered in relation to activates inhibited cholinesterase both in vitro their use as insecticides; as chemical warfare and in vivo, except that it has little or no agents; or as drugs for the treatment of ab­ effect on the enzyme in the brain. The non­ dominal distention, glaucoma, or myasthenia quaternary oximes ( such as DAM and gravis. The principal, if not the only, phar­ MINA) are able to penetrate the blood-brain macologic action of the organic phosphorus barrier. With any given inhibitor and re­ insecticides is inhibition of the enzyme activator, the extent of reactivation of cholin­ cholinesterase. The inactivity of this enzyme esterase activity depends upon how long the results in an accumulation of unhydrolyzed inhibitor and enzyme have been in contact. acetylcholine and the appearance of signs and Although the value of 2- PAM in the treat­ symptoms referable to overstimulation of the ment of organic phosphorus poisoning was parasympathetic nervous system. The drug discovered in the United States and proce­ of choice in the treatment of organophos­ dures for its use were developed here, and phorus poisoning has been atropine. Atropine although this antidote is now widely available therapy produces relief of certain symptoms for use by physicians in a number of other Durham-Hayes 42 ARCHIVES OF ENVIRONMENTAL HEALTH

countries (England, Israel, Japan, and New 15. Bergner, A D.: Histochemical Detection of Zealand), it can be purchased in this country Fatal Anticholinesterase Poisoning: II. Reactivation only by qualified physicians for clinical in­ of Cholinesterase in Cadavers of Rats, Amer. J. Path. 35 :807, 1959. vestigational use. It is unfortunate that no 16. Bergner, A. D., and Wagley, P. F. : An Effect firm has seen fit to market 2-PAM com­ of Pyridine-2-Aldoxime Methiodide (2-P AM) on mercially for prescription use in the United Cholinesterase at Motor End-Plates, Proc. Soc. Exp. States. BioI. Med. 97 :90, 1958. 17. Bethe, K.; Erdmann, W. D.; Lendle, L., Wayland J. Hayes, Jr., Chief, Toxicology Section, and Schmidt, G.: Spezifische Antidot-Behandlung Public Health Service, Communicable Disease Cen­ bei protrahierter Vergiftung mit Alkylphosphaten ter, Atlanta 22. (Paraoxon, Parathion, DFP) und Eserin und Meer­ schweinchen, N aunyn-Schmiedeberg Arch. Exp. REFERENCES Path. 231 :3, 1957. 1. Ammon, R: Die fermentative Spaltung des 17a. Brown, A W. A: Insect Control by Chemi­ Acetycholins, Pflueger Arch. Ges. Physio!. 233 :486, cals, New York, John Wiley & Sons, Inc., 1951. 1933. 18. Brown, H. V., and Bush, A F.: Parathion 2. Arnan, A.: Accidental Poisoning from Agri­ Inhibition of Cholinesterase, A.M.A Arch. Industr. cultural Pesticides, W.H.O. Ins. 12, Working Hyg. 1 :633, 1950. Paper No. 64, July 12,1961. 19. Brown, R V.: The Effects of Intracisternal 3. Arterberry, J. D.: Unpublished data. Sarin and Pyridine-2-Aldoxime Methyl Methane­ 4. Arterberry, J. D.; Durham, W. F.; Elliott, sulfonate in Anaesthetized Dogs, Brit. J. Pharmacol. J. W., and Wolfe, H. R: Exposure to Para­ 15 :170, 1960. thion: Measured by Blood Cholinesterase Level and 20. Brown, R V.; Kunkel, A M.; Somers, L. M., Urinary p-Nitrophenol Excretion, Arch. Environ. and Wills, J. H.: Pyridine-2-Aldoxime Methiodide Health 3 :476, 1961. in the Treatment of Sarin and Tabun Poisoning, 5. Askew, B. M.: Oximes and Hydroxamic Acids with Notes on Its Pharmacology, J. Pharmacol. as Antidotes in Anticholinesterase Poisoning, Brit. Exp. Ther. 120:276, 1957. J. Pharmacol. 11 :417, 1956. 21. Callaway, S., and Davies, D. R: The As­ 6. Askew, B. M.: Oximes and Atropine in Sarin sociation of Blood Cholinesterase Levels with the Poisoning, Brit. Pharmacol. 12 :340, 1957. J. Susceptibility of Animals to Sarin and Ethyl Pyro­ 7. Askew, B. M.; Davies, D. R, and Green, A. phosphate Poisoning, Brit. J. Pharmacol. 12 :382, L.: Factors Influencing the Effect of Oximes on 1957. Organophosphate-Poisoned Animals, Biochem. J. 22. Carpenter, C. P.; Wei!, C. S.; Palm, P. E.; 66 :43p, 1957. Woodside, M. W.; Nair, J. H., III, and Smyth, H. 8. Askew, B. M. ; Davies, D. R; Green, A L., and F., Jr.: Mammalian Toxicity of 1-Naphthyl-N­ Holmes, R: The Nature of the Toxicity of 2-0xo­ Methyl-Carbamate (Sevin Insecticide), Agr. Food Oximes, Brit. J. Pharmacol. 11 :424, 1956. Chern. 9 :30,1961. 9. Augustinsson, K. B. : Cholinesterases: A Study in Comparative Enzymology, Acta Physiol. Scand. 23. Childs, A F.; Davies, D. R; Green, A L., (Suppl. 52,) 15 :1, 1948. and Rutland, J. P:: Reactivation by Oximes and 10. Ball, W. L., and Kay, K.: Serum Esterase Hydroxamic Acids of Cholinesterase Inhibited by Activity as Criterion of the Toxicity of Chlorinated Organo-Phosphorus Compounds, Brit. J. Pharmacol. Hydrocarbons to Rats, AM.A Arch. Industr. 10 :462, 1955. Health 14:319, 1956. 24. Cohen, E. M., and Wiersinga, H.: Oximes 11. Barnes, J. M., and Denz, F. A: Experimental in the Treatment of Nerve Gas Poisoning: 1. Acta Demyelination with Organophosphorus Compounds, Physiol. Pharmacol. N eerl. 8 :40, 1959. J. Path. Bact. 65 :597, 1953. 25. Cohen, E. M., and Wiersinga, H.: Oximes in 12. Barstad, J. A. B.: Cholinesterase Inhibition the Treatment of Nerve Gas Poisoning: II. Acta and the Effect of Anticholinesterases on Indirectly Physiol. Pharmacol. Neerl. 9 :276, 1960. Evoked Single and Tetanic Muscle Contractions in 26. Comroe, J. H., Jr.; Todd, ]., and Koelle, G. the Phrenic-Nerve Diaphragm Preparation from the B. : The Pharmacology of Di-Isopropyl Fluorophos­ Rat, Arch. Int. Pharmocodyn. 128: 143, 1960. phate (DFP) in Man, J. Pharmacol. Exp. Ther. 13. Batchelor, G. S., and Walker, K. c.: Health 87 :281, 1946. Hazards Involved in Use of Parathion in Fruit Orchards of North Central Washington, AM.A 27. Cook, J. W.; .Blake, J. R., and Williams, M. Arch. Industr. Hyg. 10 :522, 1954. W.: The Enzymatic Hydrolysis of Malathion and 14. Beck, 1. T.: Pharmacological Study of In­ Its Inhibition by EPN and Other Organic Phos­ gested Cholinesterase, Brit. J. Pharmacol. 6 :144, phorus Compounds, J. Ass. Offic. Agr. Chemists 40 : 1951. 664, 1957. Vol. S, July, 1962 ORGANIC PHOSPHORUS POISONING 43

28. Cook, J. W.; Blake, J. R; Yip, G., and oXIme Against Organophosphorus Poisoning, Sci­ Williams, M.: Malathionase: I. Activity and In­ ence 128: 1137, 1958. hibition, J. Ass. Offic. Agr. Chemists 41 :39Y, 1958. 44a. Edson, E. F. : The Effects of Prolonged Ad­ 29. Crevier, M.; Ball, W. L., and Kay, K.: Ob­ ministration of Small Daily Doses of Parathion in servations on Toxicity of Aldrin: II. Serum the Rat, Pig, and Man, Fisons Pest Control Ltd., Esterase Changes in Rats Following Administration Nr. Saffron, Essex, England, Mimeographed Re­ of Aldrin and other Chlorinated Hydrocarbon In­ lease, March, 1957. secticides, A.M.A. Arch. Industr. Hyg. 9 :306, 1954. 45. Elliott, J. W.; Walker, K. c.; Penick, A. E., 30. Culver, D.; Caplan, P., and Batchelor, G. S.: and Durham, W. F. : Insecticide Exposure: A Sensi­ Studies of Human Exposure During Aerosol Ap­ tive Procedure for Urinary p-Nitrophenol Deter­ plication of Malathion and Chlorthion, A.M.A. mination as a Measure of Exposure to Parathion, J. Arch. Industr. Health 13 :37, 1956. Ag. Food Chern. 8 :111, 1960. 31. Davies, D. R, and Green, A. L. : The Physical 46. Epstein, M. A., and Freeman, G.: Toxicity of Chemistry of Enzymes: General Discussion, Disc. Hydroxamic Acid Analogues and Their Prophy­ Faraday Soc. 20 :269, 1955. lactic and Therapeutic Efficacy Against Nerve Gas 32. Davies, D. R, and Green, A. L.: The Kinetics Poisoning in Mice, Medical Laboratories Research of Reactivation, by Oximes, of Cholinesterase In­ Rep. No. 346, Army Chemical Center, Mal1yland, hibited by Organophosphorus Compounds, Biochem. 1955. J. 63 :529,1956. 47. Erdmann, W. D.: Parathion (E-605) Poison­ 33. Davies, D. R, and Green, A. L.: The Chemo­ ing Treated with the Antidote PAM (Pyridine-2- therapy of Poisoning by Organophosphate Anti­ Aldoxime Methiodide): Some Illustrative Cases, cholinesterases, Brit. J. Industr. Med. 16: 128, 1959. Germ. Med. Monthly 5 :304, 1960. 34. Davies, D. R, and Willey, G. L.: The 48. Erdmann, W. D., and Latki, 0.: Poison­ Toxicity of 2-Hydroxyiminomethyl-N -Methylpyri­ ing with Diisopropylfluorophosphate (DFP), Arch. dinium Methanesulphonate (P2S), Brit. J. Pharma­ Toxikol. 18:151, 1960. cal. 13 :202, 1958. 35. Davies, D. R; Green, A. L., and Willey, 49. Erdmann, W. D.; Sakai, F., and Scheler, G. L.: 2-Hydroximinomethyl-N-Methylpyridinium F.: Erfahrungen bei der spezifischen Behandlung Methanesulfonate and Atropine in the Treatment einer E-605 Vergiftung mit Atropin und dem of Severe Organophosphate Poisoning, Brit. J. Esterasereaktivator PAM, Deutsch. Med. Wschr. Pharmacal. 14:5, 1959. 83 : 1359, 1958. 36. Davison, A. N. : The Conversion of Schradan SO. Erdos, E. G.; Baart, N.; Foldes, F. F., and (0 MP A) and Parathion into Inhibitors of Cho­ Zsigmond, E. K. : Activation of Enzymatic Hydroly­ linesterase by Mammalian Liver, Biochem. J. 61: sis of Benzoylcholine by Tryptamine, Science 126: 203, 1955. 1176,1957. 37. Deichmann, W. B., and Rakoczy, R: Bus­ 51. Fleisher, J. H.; Ransa, J.; Killos, P. ]., and copan in Treatment of Experimental Poisoning by Harrison, C. G.: Effects of 1,1'-Trimethylene bis(4- Parathion, Methyl Parathion, and Systox, A.M.A. Formylpyridinium Bromide) Dioxime (TMB-4) on Arch. Industr. Hyg. 7: 152, 1953. Cholinesterase Activity and Neuromuscular Block 38. Dixon, E. M.: Dilation of the Pupils in Following Poisoning with Sarin and DFP, J. Parathion Poisoning, J.A.M.A. 163 :444, 1957. Pharmacal. Exp. Ther. 130 :461, 1960. 39. Dultz, L.; Epstein, M. A.; Freeman, G.; 52. Fleisher, J. H.; Michel, H. 0.; Yates, L., Gray, E. H., and Weil, W. B. : Studies on a Group and Harrison, C. S.: 1,l'-Trimethylene bis(4- of Oximes as Therapeutic Compounds in Sarin Formylpyridinium Bromide) Dioxime (TMB-4) Poisoning, J. Pharmacol. Exp. Ther. 119 :522, 1957. and 2-Pyridine Aldoxime Methiodide (2-PAM) as 40. Durham, W. F.: Analytical Methods for Adjuvants to Atropine in the Treatment of Anti­ Pesticides and Antibiotics, Public Health Lab. 19: cholinesterase Poisoning, J. Pharmacol. Exp. Ther. 47, 1961. 129 :31, 1960. 41. Durham, W. F.; Gaines, T. B., and Hayes, 53. Foldes, F. F.: Baart, N.; Erdos, E. G., and W. ]., Jr. : Paralytic and Related Effects of Certain Shanor, S. P.: Effect of Narcatic Analgesics and Organic Phosphorus Compounds, A.M.A. Arch. Their Antagonists on Plasma Cholinesterase, Fed. Industr. Health 13 :326, 1956. Proc. 16 :297, 1957. 42. Durham, W. F., and Wolfe, H. R: Evalua­ 54. Fournel, J. : Action antidote de l'iodomethylate tion of Exposure of Workers to Pesticides, Bull. de I'a-pyridylaldoxime vis-a-vis des intoxications W.H.O., to be published. experimentales provoquees par les insecticides or­ 43. Edery, H.: Effects of Diacetyl Monoxime on ganophosphor·es, C.R Soc. BioI. (Par.) 151 :1373, Neuromuscular Transmission, Brit. J. Pharmacol. 1957. 14:317,1959. 55. Fraser, P. J.: Acceleration of the Enzymic 44. Edery, H., and Schatzberg-Porath, G. : Hydrolysis of Benzoylcholine, Brit. J. Pharmacol. Pyridine-2-Aldoxime Methiodide and Diacetyl Mon- 11 :7, 1956. Durham-Hayes 44 ARCHIVES OF ENVIRONMENTAL HEALTH

56. Frawley, ]. P.; Fuyat, H. N.; Hagan, E. C; 73. Hawkins, R. D., and Mendel, B.: Selective Blake, ]. R., and Fitzhugh, O. G. : Marked Potentia­ Inhibition of Pseudocholinesterase by Di-Isopropyl tion in Mammalian Toxicity from Simultaneous Fluorophosphate, Brit. J. Pharmacol. 2 :173, 1947. Administration of 2 Anticholinesterase Compounds, 74. Hayes, W. J.. Jr., and Durham, W. F.: ]. Pharmacol. Exp. Ther. 121 :96, 1957. Studies of Organic Phosphorus Insecticide Poison­ 57. Fredriksson, T.: Further Studies on Fluoro­ ing, VI Congreso International de Pathologia Com­ phosphorylcholines: Pharmacological Properties of parada: II, 1952; Acta, 1954, p. 231. 2 New Analogues, Arch. Int. Pharmocodyn. 115: 75. Hestrin, S.: The Reaction of Acetylcholine 474, 1958. and Other Carboxylic Acid Derivatives with Hy­ 58. Fredriksson, T.: Studies on the Percutaneous droxylamine and Its Analytical Application, ]. BioI. Absorption of Sarin and 2 Allied Organophos­ Chem. 180 :249, 1949. phorus Cholinesterase Inhibitors, Acta Derma­ 76. Hobbiger, F. : Reactivation of Phosphorylated tovener (Stockh.) (Suppl. 41) 38 :9, 1958. Plasma Cholinesterase by Nicotinhydroxamic Acid 59. Fredriksson, T.; Hansson, C, and Holmstedt, Methiodide, Congress International Biochemistry, B.: Effects of Sarin in the Anaesthetized and Un­ Abstracts, 3d Congress, Brussels, 1955, p. 30. anaesthetized Dog Following Inhalation, Percuta­ 77. Hobbiger, F.: Chemical Reactivation of Phos­ neous Absorption, and Intravenous Infusion, Arch. phorylated Human and Bovine True Cholinestera'Ses, Int. Pharmocodyn. 126 :288, 1960. Brit. ]. Pharmacol. 11 :295, 1956. 60. Freedman, A. M.; Willis, A., and Himwich, 78. Hobbiger, F.: Protection Against the Lethal H. E.: Correlation Between Signs of Toxicity and Effects of Organophosphates by Pyridine-2-Aldox­ Cholinesterase Level of Brain and Blood During ime Methiodide, Brit. ]. Pharmacol. 12 :438, 1957. Recovery from Di-Isopropylfluorophosphate (DFP) 79. Hobbiger, F.; O'Sullivan, D. G., and Sadler, Poisoning, Amer. J. Physiol. 157 :80, 1949. P. W.: New Potent Reactivators of Acetylcho­ 61. Freeman, G., and Epstein, M. A. : Therapeutic linesterase Inhibited by Tetraethyl Pyrophosphate, Factors in Survival After Lethal Cholinesterase Nature 182 :1498, 1958. Inhibition by Phosphorus Insecticides, New Engl. 80. Hobbiger, F., and Sadler, P. W.: Protection ]. Med. 253 :266, 1955. by Oximes of bis-Pyridinium Ions Against Lethal 62. Funchs, A. ].: Treatment of Severe Para­ Diisopropyl Phosphorofluoridate Poisoning, Nature thion Poisoning with 2-Pyridine-Aldoxime Methio­ 182: 1672, 1958. dide (2-P AM), Arch. Environ. Health 1 :404, 1960. 81. Hobbiger, F., and Sadler, P. W.: Protec­ 63. Funckes, A. ].: Unpublished data. tion Against Lethal Organophosphate Poisoning by 64. Gaines, T. B.: Personal communication to the Quaternary Pyridine Aldoximes, Brit. ]. Pharmacol. author. 14:192,1959. 65. Gordon, A. S., and Frye, C W.: Large Doses 82. Holmes, R., and Robins, E. L.: The Reversal of Atropine: Low Toxicity and Effectiveness in by Oximes of Neuromuscular Block Produced by Anticholinesterase Intoxication, ].A.M.A. 159 :1181, Anticholinesterases, Brit. ]. Pharmacol. 10 :490, 1955. 1955. 66. Grob, D., and Harvey, A. M. : The Effects and 83. Holmstedt, B.: Synthesis and Pharmacol­ Treatment of Nerve Gas Poisoning, Amer. ]. Med. ogy of Dimethylamide-Ethoxy-Phosphoryl Cyanide 14 :52, 1953. (Tabun) Together with a Description of Some 67. Grob, D., and Johns, R. ].: Treatment of Anti­ Allied Anticholinesterase Compounds Containing the cholinesterase Intoxication with Oximes, ].A.M.A. N-P Bond, Acta Physiol. Scand. 25:1,1951. 166: 1855, 1958. 84. Holmstedt, B.: Pharmacology of Organo­ 68. Grob, D., and Johns, R. ].: Use of Oximes in phosphorus Cholinesterase Inhibitors, Pharmacol. the Treatment of Intoxication by Anticholinesterase Rev. II :567, 1959. Compounds in Normal Subjects, Amer. ]. Med. 24: 85. Imo, K.: Treatment of E-605 Poisoning with 497, 1958. Atropine and PAM, Medizinische No. 44 :2114, 1959. 69. Grob; D., and Johns, R. ].: Use of Oximes in 86. Jacques, R., and Bein, H. ].: Toxicology the Treatment of Intoxication by Anticholinesterase and Pharmacology of aNew Systemic Insecticide Componnds in Patients with Myasthenia Gravis, of the Phosphoric Acid Ester Type, Phosphamidon Amer . .r. Meei. 24:512,1958. (2- Chloro-2-Diethylcarbamoyl-l-Methylvinyldi­ 70. Grob, D.; Lilienthal, J. L.; Harvey, A. methyl-Phosphate), Arch. Toxikol. 18 :316, 1960. M., and Jones, B. F.: The Administration of Di­ 87. Jager, B. V., and Stagg, G. N.: Toxicity of Isopropyl Fluorophosphate (DFP) to Man, Bull. Diacetyl Monoxime and of Pyridine-2-Aldoxime Johns Hopkins Hosp. 81 :217, 1947. Methiodide in Man, Bull. Johns Hopkins Hosp. 102: 71. Hamblin, D.O., and Marchand, ]. F.: Para­ 203, 1958. thion Poisoning, Amer. Practit. 2 :1, 1951. 88. Jager, B. V.; Stagg, G. N.; Green, N., and 72. Hardegg, 'vV., and Schaeffer, N. : Zur Kinetik Jager, L.: Studies on Distribution and Disappear­ der Cholinesterasen, Pflueger Arch. Ges. Physiol. ance of Pyridine-2-Aldoxime Methiodide (PAM) 255: 136, 1952. and of Diacetyl Monoxime (DAM) in Man and Vof. 5, J ufy, 1962 ORGANIC PHOSPHORUS POISONING 45

in Experimental Animals, Bull. Johns Hopkins 105. McNamara, B. P.; Murtha, E. F.; Bergner, Hosp. 102 :225, 1958. A. D.; Robinson, E. M.; Bender, C. W., and Wills, 89. Kariog, 0.; Nimb, M., and Poulsen, E.: ]. H.: Studies on the Mechanism of Action of Parathion Poisoning Treated with Picoline-2- DFP and TEPP, J. Pharmacol. Exp. Ther. 110: Aldoxime Iodide, Ugeskr. Laeg. 120 :177, 1958. 232, 1954. 90. Kewitz, H.: A Specific Antidote Against 106. Metcalf, R. L.: The Colorimetric Micro­ Lethal Alkyl Phosphate Intoxication: III. Repair Estimation of Hum:m Blood Cholinesterases and Its of Chemical Lesion, Arch. Biochem. 66 :263, 1957. Application to Poisoning by Organic Phosphate In­ 91. Kewitz, H., and Nachmansohn, D.: A Spe­ secticides, J. Econ. Entomol. 44:883, 1951. cific Antidote Against Lethal Alkyl Phosphate In­ 107. Michel, H. 0.: An Electrometric Method toxication: IV. Effects in Brain, Arch. Biochem. for the Determination of Red Blood Cell and 66 :271, 1957. Plasma Cholinesterase Activity, ]. Lab. Clin. Med. 92. Kewitz, H., and Wilson, 1. B.: A Specific 34: 1564, 1949. Antidote Against Lethal Alkylphosphate Intoxica­ 108. Milosevic, M. P.; Terzic, M., and Vojvodic, tion, Arch. Biochem. 60 :261, 1956. V. : Protection Against Lethal Phosphamidone 93. Kewitz, H.; Wilson, 1. B., and Nachmansohn, Poisoning by N,N' -Trimethylene-bis (4-Hydroxy­ D.: A Specific Antidote Against Lethal Alkyl minomethyl-Pyridinium Bromide) (TMB-4), Arch. Phosphate Intoxication: II. Antidotal Properties, Int. Pharmacodyn. 132 :180, 1961. Arch. Biochem. 64 :456, 1956. 109. Murphy, S. D.; Anderson, R. L., and Du­ 94. Koelle, G. B., and Gilman, A.: The Chronic bois, K. P.: Potentiation of Toxicity of Malathion Toxicity of Di-Isopropyl Fluorophosphate (DFP) by Triorthotolyl Phosphate, Proc. Soc. Exp. BioI. in Dogs, Monkeys, and Rats, J. Pharmacol. Exp. Med. 100 :483, 1959. Ther. 87 :435, 1946. 110. Myers, D. K.: Effect of Salt on the Hy­ 95. Koelle, G. B., and Gilman, A.: Anticholin­ drolysis of Acetylcholine by Cholinesterases, Arch. esterase Drugs, J. Pharmacol. Exp. Ther. 95 :166 Biochem. Biophys. 37 :469, 1952. (April, Pt. 2) 1949. 111. Nachmansohn, D., and Wilson, 1. B.: Trends 96. Koelle, G. B., and Steiner, E. c.: The Cere­ in the Biochemistry of Nerve Tissue: Currents in bral Distributions of a Tertiary and a Quaternary Biochemical Research, 1956, New York, Intersci­ Anticholinesterase Agent Following Intravenous ence Publishers, Inc., 1956, p. 628. and Intraventricular Injection, J. Pharmacol. Exp. 112. Namba, T.: Oxime Therapy for Poisoning Ther. 118 :420, 1956. by Alkylphosphate-Insecticides, Proceedings, 13th 97. Koster, R.: Synergisms and Antagonisms Be­ International Congress Occupational Health, July tween Physostigmine and Di-Isopropyl Fluoro­ 25-29, 1960. phosphate in Cats, J. Pharmacol. Exp. Ther. 88: 113. N amba, T.: Toxicity of PAM (Pyridine-2- 39, 1946. Aldoxime Methiodide), unpublished data. 98. Krivoy, W. A., and Wills, J. H.: Adaptation 114. Namba, T., and Hiraki, K.: PAM (Pyri­ to Constant Concentrations of Acetylcholine, J. dine-2-Aldoxime Methiodide) Therapy for Alkyl­ Pharmacol. Exp. Ther. 116 :220, 1956. phosphate Poisoning, ].A.M.A. 166 :1834,1958. 99. Lehman, R. A., and Nicholls, M. E.: An­ 115. Neubert, D., and Schaefer, ].: Loss of tagonism of Phospholine (Echothiophate) Iodide Diethyl-p-Nitrophenyl Phosphate and Octamethyl­ by Certain Quaternary Oximes, Proc. Soc. Exp. pyrophosphoramide Activities After Pretreatment BioI. 104: 550, 1960. with a-Hexachlorocyclohexane, N aunyn-Schmiede­ 100. Limperos, G., and Ranta, K. E.: A Rapid berg Arch. Exp. Path. 233:151,1958. Screening Test for the Determination of the Ap­ 116. O'Brien, R. D.: Toxic Phosphorus Esters: proximate Cholinesterase Activity of Human Blood, Chemistry, Metabolism and Biologic Effects, New Science 117 :453, 1953. Yark and London, Academic Press, Inc., 1960. 101. Longo, V. G.; Nachmansohn, D., and Bovet, 117. O'Brien, R. D., and Davison, A. N.: An­ D.: Electroencephalographic Aspects of the Antag­ tagonists to Schradan Poisoning in Mice, Canad. ]. onism Between 2-Pyridine-Aldoxime Iodomethylate Biochem. 36: 1203, 1958. (2-P AM) and Isopropyl Methylfluorophosphate 118. O'Leary, ]. F.; Kunkel, A. M., and Jones, (Sarin), Arch. Int. Pharrnocodyn. 123 :282, 1960. A. H.: Efficacy and Limitations of Oxime­ 102. Loomis, T. A.: The Effect of an Aldoxime Atropine Treatment of Organophosphorus Anti­ on Acute Sarin Poisoning, J. Pharmacol. Exp. Ther. cholinesterase Poisoning, ]. Pharmacol. Exp. Ther. 118: 123, 1956. 132:50,1961. 103. Loomis, T. A.: Unpublished observations, 119. Poziomek, E. ].; Hackley, B. E., J r., and 1958. Steinberg, G. M.: Pyridinium Aldoximes, ]. Org. 104. Marchand, J. F.: Microtests for Cholines­ Chern. 23 :714, 1958. terase: Interpretation After Nerve Gas or Agri­ 120. Quinby, G. E., and Brown, H.: Paper pre­ cultural Insecticide Exposures, J.A.M.A. 149 :738, sented at University of Washington Hosp!tal, Clini­ 1952. cal Pathological Conferente, May, 1961. Durham-Hayes 46 ARCHIVES OF ENVIRONMENTAL HEALTH

121. Quinby, G. E., and Clappison, G. B.: Para­ phorylcholines, Proceedings of the 4th International thion Poisoning: A Near-Fatal Pediatric Case Congress of Biochemistry, Vienna, 1958. Treated with Pyridine Aldoxime Methiodide 139. Todrick, A.; Fellowes, K. P., and Rutland, (2-PAM), Arch. Environ. Health 3 :538,1961. ]. P.: The Effect of Alcohols on Cholinesterase, 122. Quinby, G. E., and Congdon, R. S.: Un­ Biochem. ]. 48 :360, 1951. published data. 140. Up holt, W. M.; Quinby, G. E.; Batchelor, 123. Quinby, G. E., et al.: Unpublished data. G. S., and Thompson, ]. P.: Visual Effects Ac­ 124. Rajapurkar, M. V., and Panjwani, M. H.: companying TEPP-Induced Miosis, A.M.A. Arch. The Action of Diacetylmonoxime (DAM) on Cili­ Ophthal. 56: 128, 1956. ary Activity, Arch. Int. Pharmacodyn. 131 :107, 141. Verhulst, H. L., and Page, L. A.: A New 1961. Agent in Parathion Poisoning, ]. New Drugs 1 :80, 125. Rosen, F.: Toxic Hazards: Parathion, New 1961. Engl. ]. Med. 262: 1243, 1960. 142. von Kaulla, K., and Holmes, ]. H.: Changes 126. Rosenberg, P.: In Vivo Reactivation by Following Anticholinesterase Exposures: Blood PAM of Brain Cholinesterase Inhibited by Para­ Coagulation Studies, Arch. Environ. Health 2: 168, oxon, Biochem. Pharmacol. 3 :212, 1960. 1961. 127. Rothe, et al.: Manuscript in preparation. 143. Wagner-Jauregg, T., and Hackley, B. E., 128. Rutland,]. P.: The in Vivo Effects of Some Jr.: Model Reactions of Phosphorus-Containing Oximes in Sarin Poisoning, Biochem. ]. 66 :43P, Enzyme Inactivators: III. Interaction of Imidazole, 1957. Pyridine, and Some of Their Derivatives with Di­ 129. Salerno, P. R., and Coon, ]. M.: Drug Pro­ alkyl Halogeno-Phosphates, ]. Amer. Chem. Soc. tection Against the Lethal Action of Parathion, 75 :2125, 1953. Arch. Int. Pharmacodyn. 84 :227, 1950. 144. Wagner-Jauregg, T.; Hackley, B. E., Jr.; 130. Sanderson, D. M.: Treatment of Poisoning Lies, T. A.; Owens, O. 0., and Proper, R.: Model by Anticholinesterase Insecticides in the Rat, J. Reactions of Phosphorus-Containing Enzyme Inac­ Pharm. Pharmacol. 13 :435, 1961. tivators: IV. The Catalytic Activity of Certain 131. Sanderson, D. M., and Edson, E. F.: Oxime Metal Salts and Chelates in the Hydrolysis of Di­ Therapy in Poisoning by 6 Organophosphorus In­ isopropyl Fluorophosphate, ]. Amer. Chem. Soc. secticides in the Rat, ]. Pharm. Pharmacol. 11 :721, 77 :922, 1955. 1959. 145. Wills, J. H.: Recent Studies of Organic 132. Schvartsman, S.; Goyos Carlini, M. P., and Phosphate Poisoning, Fed. Proc. 18 :1020,1959. Pereira de Silva, W. B.: Treatment of Poisonings 146. Wills, ]. H., and Borison, H. L.: Modifica­ with Organophosphorus Insecticides, ]. Bras. Med. tion by Sarin and Antagonists of Medullary Re­ 3 :673, 1960. spiratory Activities, Fed. Proc. 18 :459, 1959. 132a. Seifert, P.: Giftmort mit E-605 an einem 147. Wills, J. H.; Kunkel, A. M.; Brown, R. V., Saug1ing, Arch. Toxikol. 15 :80, 1954. and Groblewski, G. E. : Pyridine-2-Aldoxime 133. Seume, F. W., and O'Brien, R. D.: Poten­ Methiodide and Poisoning by Anticholinesterases, tiation of the Toxicity to Insects and Mice of Science 125 :743, 1957. Phosphorothionates Containing Carboxyester and 148. Wilson, I. B.: Acetylcholinesterase: XI. Carboxyamide Groups, Toxicol. Appl. Pharmacol. Reversibility of Tetraethyl Pyrophosphate Inhibi­ 2 :495, 1960. tion, ]. BioI. Chem. 190:111,1951. 134. Smallman, B. N., and Wolfe, L. S.: The 149. Wilson, I. B.: Acetylcholinesterase: XIII. Effect of Salts on the Estimation of Cholinesterase Reactivation of Alkyl Phosphate-Inhibited Enzyme, Activity, Enzymologia 17 :133, 1954. ]. BioI. Chem. 199: 113, 1952. 135. Sumerford, W. T.; Hayes, W. ]., Jr.; 150. Wilson, I. B.: Reactivation of Enzymes In­ Johnston, J. M.; Walker, K., and Spillane, ].: hibited by Certain Highly Toxic Agents, Science Cholinesterase Response and Symptomatology from 120:790,1954. Exposure to Organic Phosphorus Insecticides, 151. Wilson, I. B.: Reactivation of Human Se­ A.M.A. Arch. Industr. Hyg. 7 :383, 1953. rum Esterase Inhibited by Alkylphosphates, ]. 136. Sundwall, A.: Plasma Concentration Curves Amer. Chem. Soc. 77 :2383, 1955. of N-Methyl-Pyridinium-2-A1doxime Methane Sul­ 152. Wilson, I. B.: Designing of a New Drug fonate (P2S) After Intravenous, Intramuscular, with Antidotal Properties Against the Nerve Gas and Oral Administration in Man, Biochem. Phar­ Sarin, Biochim. Biophys. Acta 27: 196, 1958. macol. 5 :225, 1960. 153. Wilson, I. B., and Bergmann, F.: Studies 137. Tagaki, H.: Activation of Specific Cholin­ on Cholinesterase: VII. The Active Surface of esterase by Tetraethyl Ammonium Bromide and a Acetylcholine Esterase Derived from Effects of pH New Differentiation of Types of Cholinesterase, on Inhibitors, ]. BioI. Chem. 185 :479, 1950. Folia Pharmacol. J ap. 49 :435, 1953. 154. Wilson, I. B., and Ginsburg, S.: A Power­ 138. Tammelin, L. E., and Enander, I.: Reacti­ ful Reactivator of Alkylphosphate-Inhibited Acetyl­ vation of Cholinesterase Inhibited by Organophos- cholinesterase, Biochim. Biophys. Acta 18: 168, 1955. Vol. 5, July, 1962 ORGANIC PHOSPHORUS POISONING 47

155. Wilson, 1. B., and Sondheimer, F.: A Spe­ 158. Woodard, G. T.: The Treatment of Organic cific Antidote Against Lethal Alkyl Phosphate In­ Phosphate Insecticide Poisoning with Atropine Sul­ toxication: V. Antidotal Properties, Arch. Biochem. fate and 2-PAM (2-Pyridine-Aldoxime Methio­ Biophys. 69 :468, 1957. dide) , Vet. Med. 52:571, 1957. 156. Wislicki, L.: Differences in the Effect of 159. Summerson, W. H.: Progress in the Bio­ Oximes on Striated Muscle and Respiratory Centre, chemical Treatment of Nerve Gas Poisoning, Arch. Int. Pharmocodyn. 129: 1, 1960. 157. Wood, J R.: Medical Problems in Chemi­ Armed Forces Chem. J., Jan.-Feb., 1955. cal Warfare, JA.M.A. 144 :606, 1950. 160. Yamamoto, S.: Unpublished data.

Reproduced with Permission by the DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE From the Archives of Environmental Health, Vol. 5, pp. 21-47, July 1962

Copyright 1962, by American Medical Association

Dttrham-Hayes Reprinted From The Journal of The American Medical Association July 28,1962, Vol. 181, pp. 332 and 333 Copyright 1962, by American Medical Association

HEALTH HAZARDS OF PESTICIDES inhibition of the enzyme cholinesterase. This results in an accumulation of unhydrolyzed acetylcholine he pesticide-related problem t~at the average and. therefore, in signs and symptoms referrable to Tphysician is most likely to face and about over-stimulation of the parasympathetic nervous which he must take immediate and definitive action system. The drug of choice in the treatment of or­ is acute poisoning due to occupational or accidental ganophosphorus poisoning has been atropine, exposure or to suicidal ingestion. which relieves certain symptoms by pharmacologiC Almost every pesticide can cause poisoning if it blocking of the action of acetylcholine. Atropine, is swallowed. For many years and at least as late however, has no effect on the basic, biochemical as 1959, the arsenicals caused more accidental pathology involved in anticholinesterase poisoning. deaths than any other group of pesticides. This is Furthermore, it has no effect on the nicotinic action almost certainly due to the casualness with which of acetylcholine although it is effective in treating they are still stored and the ease with which they those symptoms referrable to the central and mus­ can be found and ingested by children and other carinic actions of this neurohumor. uninformed people. The arsenical pesticides have More recently a series of antidotes has been de­ never been an important source of occupational veloped that can reverse the combination between disease. Among the newer pesticides, greatest at­ the cholinesterase molecule and the inhibitor. tention has focused on the chlorinated hydrocarbon These compounds are oximes. The outstanding and the organic phosphorus insecticides. Although members of this group are the salts of 2-pyridine the chlorinated hydrocarbons have caused a mod­ aldoxime, including the methiodide (2-PAM io­ erate number of cases of accidental posioning, their dide ), the methochloride (2-PAM chloride), and record of occupational safety is generally good. In the ethanesulfonate (P2S). 2-PAM chloride is sold fact, the great amount of study they continue to in the United States by the Campbell Pharmaceuti­ receive is justified almost exclusively by their per­ cal Company, Inc., 121 East 24th St., New York sistence as residues on treated crops and their rela­ City; under the trade name Protopam. This drug is tively prolonged storage in the tissues of domestic marketed under a limited license for sale to quali­ animals and man. However, careful regulation has fied physicians for clinical investigations only. p.revented the residues from offering anything but a Emergency supplies are available at some poison­ potential problem. There is no confirmed record of control centers, at many medical schools, or from clinical effect from eating food treated with pesti­ the U.S. Public Health Service laboratories in At­ cides according to approved agricultural practice. lanta, Ga., Wenatchee, Wash., and Phoenix, Ariz. From the standpoint of occupational hazard, the In the July issue of the At-chives of Environ­ more toxic organic phosphorus insecticides are the mental Health (p. 21) there is a review by Wil­ outstanding offenders among the newer agricultural liam F. Durham and Wayland J. Hayes, Jr., on the chemicals. This is true in spite of the strict regula­ therapy of organic phosphorus poisoning. Special tion imposed on them from the beginning. This attention is given in this review to compounds that regulation and the extensive educational campaign reactivate inhibited choliJ;lesterase and to their that has accompanied their introduction and use proper clinical use in combination with atropine. undoubtedly have restricted both occupational and Extensive animal research on salts of 2-pyridine accidental poisoning by these compounds. Granted aldoxime has been completed. Well-documented, that all noncriminal poisoning can be traced to clinical use of these compounds in more than 40 "carelessness," the growing importance of the more cases of parathion poisoning has established their toxic organic phosphorus insecticides as reported effectiveness and safety for this purpose. More lim­ causes of occupational disease 1 is almost certainly ited experience indicates their value in the treat­ due to the tremendous increase in their use, to their ment of poisoning by some other organic phos­ inherent toxicity, and to the ease with which many phorus compounds. of them are absorbed through the skin. Detailed information on the clinical use of these Two factors specifically favor success in the treat­ drugs is now available to physicians through the ment of poisoning with the organic phosphorus above-mentioned review. For maximum usage to compounds, i.e., the short duration of the emer­ be made of the considerable knowledge now avail­ gency and the existence of effective antidotes. The able on treatment of anticholinesterase poisoning, it acute episode lasts only from 24 to 48 hours. Most is necessary that one of these oxime salts be made deaths occur within the first 24 hours, and if a pa­ generally available for prescription by physicians in tient survives this long, he usually recovers com­ the United States. pletely. The principal pharmacologic action of the or­ 1. Kleinman, C. D.; West, I.; and Augustine, M. S.: Occupational Disease in California Attributed to Pesticides and Agricultural Chemi­ ganic phosphorus insecticides, if not the only one, is cals, Arch Environ Health 1:118, 1960. Printed in U.S.A.