Postgrad Med J: first published as 10.1136/pgmj.55.646.556 on 1 September 1979. Downloaded from Postgraduate Medical Jouirnal (August 1979) 55, 556-559

CASE REPORTS Toxic psychosis with antihistamines reversed by physostigmine P. J. COWEN B.Sc., M.B.

Department of Psychological Medicine, King's College Hospital, Denmark Hill, London SE5 9RS

Summary who was walking unsteadily around the ward pour- A case of toxic psychosis due to antihistamine - ing water from a jug over patients and furniture. ing is described. The reversal of this state by physo- She was confused, disorientated in time and place, supports the contention that it is caused by and had visual hallucinations. an syndrome. The management of There was no previous history of psychiatric ill- antihistamine poisoning is discussed. ness. A diagnosis of a drug-induced toxic con- fusional state with features of an anticholinergic Introduction syndrome was made. She was given i.m, physostig- mine salicylate 0 5 mg, and within 15 min was calm

Toxic psychosis is a recognized complication of Protected by copyright. antihistamine poisoning (Goodman and Gilman, and able to orientate herself spatially and temporally. 1975). It has been suggested that this toxic state There was no evidence of confusion or visual might be caused by anticholinergic mechanisms and hallucinations. After 2 hr she again became drowsy that treatment with physostigmine could reverse it and confused but remained quiet and did not present (Granacher and Baldessarini, 1975). Despite this, a nursing problem. Three hours later she was given physostigmine is not usually recommended in the night sedation of one g oral chlormethiazole and management of antihistamine poisoning. A case is slept until the following morning. She was then lucid now reported of antihistamine poisoning which was and orientated with little memory for the confusional complicated by marked central symptoms. These episode. Her mental state remained stable and she symptoms were abolished by physostigmine sali- was subsequently discharged to attend the psychia- cylate. tric out-patient clinic. Discussion Case report The central effects of antihistamines constitute

A 40-year-old housewife was admitted to the their greatest danger in acute poisoning. The pre- http://pmj.bmj.com/ medical ward having taken an unknown number of sentation may vary from confusion, hallucinations promethazine tablets. She was deeply unconscious and convulsions to deepening coma and respiratory and responded only in a sluggish and inco-ordinated arrest. Peripheral effects of poisoning include fixed manner to pain. Her pulse was 104 beats/min. Her dilated pupils, tachycardia, flushed skin and pyrexia pupils were dilated and did not react to light. The (Goodman and Gilman, 1975). deep tendon reflexes were present and symmetrical In addition to H1-receptor blocking properties, but both plantar responses were extensor. Gastric antihistamines also possess peripheral and central Javage had been performed in Casualty and 100 mEq anticholinergic effects (Goodman and Gilman, 1975). on September 26, 2021 by guest. of sodium bicarbonate lefi in the stomach. Routine It is becoming increasingly recognized that drugs obervations were made and nursing care given. whose properties include anticholinergic activity Six hours after admission her level of conscious- may, in acute poisoning, produce a picture typical ness had improved so that she was rousable but of peripheral and central anticholinergic . increasingly restless and difficult to nurse. Her fluid Such drugs include the tricyclic antidepressants intake was poor and she was aggressive when and phenothiazines as well as more obvious examples approached. This state continued for the next 24 hr such as belladonna and anti-Parkinson during which she received 2 i.m. doses of chlorpro- agents (Granacher and Baldessarini, 1975). mazine 100 mg and 2 i.m. doses of 10 mg Toxic anticholinergic effects may be reversed by wvithout effect. Psychiatric assessment was requested. treatment with a suitable anticholinesterase. Physo- Examination showed a restless, agitated woman stigmine is most commonly used because in contrast 0032-5473/79/0800-0556 502.00 ©) 1979 The Fellowship of Postgraduate Medicine Postgrad Med J: first published as 10.1136/pgmj.55.646.556 on 1 September 1979. Downloaded from Case reports 557 to it passes the blood-brain barrier and peated doses may be needed. Physostigmine should reverses both central and peripheral anticholinergic be used with caution in patients who have an under- blockade (Duvoisin and Katz, 1968). The value of lying condition such as heart block or asthma which physostigmine in poisoning is well known, would contra-indicate excessive stimu- and more recent reports have described its role in lation (Granacher and Baldessarini, 1975). In these the treatment of tricyclic antidepressant (Janson, patients, central excitement is best controlled with Watt and Hermos, 1977) and phenothiazine poison- sedatives which lack anticholinergic effects, for ing (Wang and Marlowe, 1977). It appears that anti- example chlormethiazole or diazepam. Chlorpro- histamines, too, may produce an anticholinergic mazine does possess anticholinergic activity and syndrome. Indeed, most if not all of the clinical should be avoided. features of antihistamine poisoning are attributable to anticholinergic toxicity. The reversal by physo- References stigmine of the delirium described in the case report DuvoIssN, R.C. & KATZ, R. (1968) Reversal of central anti- supports this contention. In addition, physostigmine cholinergic syndrome in man by physostigmine. Journal of has been shown to reverse central excitement and the American Medical Association, 206, 1963. GOODMAN, L.S. & GILMAN, A. (1975) The Pharmacological depression following antihistamine premedication Basis of Therapeutics. 5th edn, p. 603. MacMillan, New (Lee, Turndorf and Poppers, 1975). York. Antihistamine poisoning in adults is not usually GRANACHER, R.P. & BALDESSARINI, R.J. (1975) Physostig- a life-threatening event, and simple supportive mine: Its use in acute anticholinergic syndrome with anti- depressant and antiparkinson drugs. Archives of General measures are adequate (Goodman and Gilman, Psychiatry, 32, 375. 1975). In children and more severely poisoned adults JANSON, P.A., WATT, J.B. & HERMOS, J.A. (1977) central complications are frequent, and it is here that overdose: Success with physostigmine and failure with physostigmine may play a useful role. Features of neostigmine in reversing toxicity. Journal of the American Medical Association, 237, 2632. Protected by copyright. the anticholinergic syndrome such as confusion, LEE, J.H., TURNDORF, H. & POPPERS, P.J. (1975) Physo- coma and convulsions may be expected to respond stigmine reversal of antihistamine-induced excitement and (Rumack, 1973) and, in addition, peripheral anti- depression. Anesthesiology, 43, 683. cholinergic blockade will be reversed. Because of RUMACK, B.H. (1973) Anticholinergic poisoning: Treatment with physostigmine. Pediatrics, 52, 449. the short half-life of physostigmine, demonstrated WANG, S.F. & MARLOWE, C.L. (1977) Treatment of pheno- by the return of symptoms in the case report, re- thiazine overdose with physostigmine. Pediatrics, 59, 301. http://pmj.bmj.com/ on September 26, 2021 by guest.