EXPERIMENTAL AND CLINICAL EXPERIENCE WITI~ TOXIFERINE ( OF CAL]ABASH )*

R. FREV, M.D., F.F.A.R.C.S., and R. SEEGER, M.D.]"

T•E PRESENT DRUGS do not vet fulfil all the desires of the anaesthetist with regard to variation o~ the dur~tion of action, the t~ossibility of being antagonized, and the avoidance of ,side-effects. The search fdr further relaxant drugs is therefore justified. In 1958, Karrer and Schmid (Ztirich) isolated the chief from Calabash curare and determined their chemical structure. Waser investigated their 0phar- macological properties and subsequentlyl, , together with the anaesthetistl Harbeck '(Zfirich), defined the possibilities of their clinical use. In order to form our own opinion, we use d Toxiferine, the drug which is per- : . 9 ~ - , I haps the most appropriate for clinical use, in ;~0 trials on conscious volm~teers and 100 patients during anaesthesia, in the I)epartment of Anaesthesia of the University Clinics, Mainz.

~'I ETHODS Auto Trials (a) Volunteers. The three volunteers were assistants in the Department of Anaesthesia who were familiar with the action of .muscle relaxants because, in the anaesthesiological practice, they had workecl daily with such drugs for years. Thus we could rely on the co-operation of the volunteers and were able to suffi- ciently exclude any subjective influence on the results by the volunteers. In order to determine the relationship between e~ffect and body weight, we chose volunteers (of about the same age) who differed markedl3~ in body weight (44, 63, and 82 kg.). (b) Technique of injection. The Toxiferii}e solution was adliainistered intra- venously. The injection time varied between 15 and 90 sec. We chose the,extremely rapid injection of five seconds in order to achieve a high initial blood level enabling us, at the same time, to obtain a better understanding of possible side effects. The slower injection was studied because this lies nearer the-rrrode of administration under clinical conditions or represents the pharmacologically appropriate ha ode of administration. In varying the speed of injection of the same dose, we were able to demonstrate variations in the intefisity an.~ duration of action with Toxiferine, .'as expected ~rom experience with ottaer curare preparations. (c) Form and technique of recording. Blood pressure, pulse rate, vitat capacity:, respiratory rate, and grip strength were recorded at intervals of pine to two *Paper read at the X,Vorld Congress of Anaesthesi01ogisl.s in Toronto, Sept. 8, 1960. ~Department of Anaesthesia of the University Clinics, Nlainz (Director: Professor .R-. Frey, M.D., F.F.A.R.C.S.). 99 Can. Anaes. Soc. J., vol. 8, no. 2, March, 1961. 100 CANADIAN ANAESTHETISTS' SOCIETY JOURiNAL minutes, iln addition, we registered the latent period, th~ duration of head drop and of of deglutition which is so importan~ in" clinical - . application. - The grip strength was measured with the ergometer, the yital capacity with the volumeter of the anaesthetic apparatus (Draeger). W_le purposely renounced further spirographic measurements, firstly because additional recordings would have been impossibte without prolonging the test perioc]s and secondly because we did not want to overtwe the volunteers; both would have impaired the accuracy of the results.

Clinical A ppli, cation (a) Clinical material. The only criteria for the ~elec~ion of patients for the clinical use of Toxiferine was the duration 6f the intended operative interven- tion, that is, whether an operation of more than ony to two hours ' duratlo " n was anticipated. Age, general condition, or concomitantdiseases (if these ,permitted curarization at all) were not taken into consideration. Our clinical material, therefore,, consisted mainly of middte-aged to elderly adults. The drug was rarely administered to children, chiefly because such prolonged operations are less frequent in children. Toxiferine has not been given to infants or small children. (b)-Operalions. The drug" was used in long operations,, mainly abdominal and thoracic surgery, such as partial gastrectomv (ilnclu~ting bleeding and per- forated ulcers), total gas:trectomy, splenectomy, hemicolectomy, amputation,of the rectum, cholecystectomy with choledochotomy for which a rather long operation was to be anticipated, resection of the pancreas, pneumonectomy, lobectomy, and resection of the esophagus and cardia. In addition, Toxiferine was used in the resection of advanced goitre and, less flrequently, in protracted orthopaedic interventions, such as pseudo~irthrosis, open reduction of old frac- tures; and so on, whenever strong curarization seemed appropriate; riot every surgeon wishes it. In urological operations we were more reserved: although we used Toxiferine without hesitation in operations for ureteral or renal calculi, or plastic surgery of the renal pelvis in patients in whom the appropriate investigations indicated intact renal function, we preferred not to use Toxiferine in patients in whom this could not be assumed. It is known--from animal experiments that Toxiferine --as Other synthetic non-depolarizing relaxants--is not reduced, but excreted quantitatively through the kidneys almost unchanged. C~. Technique of A~aestkesia. Our anaesthetic procedUr~ was as follows: after premedication with meperidine and atropine, anaesthesia was induced intra- venouslywith thiopental, intubation was then performed under succinylcholine apnoea. Anaesthesia was maintained with a N=O-0.2 mixture with or without the addition of small amounts of . After the return of spontaneous respiration, Toxiferine was administered intravenously in a close which produced complete paralysis of the Spontaneous respiration o1: at least to such a degree that.respiration could be controlled without resistance. In children, instead of intubation under succ.in~qcholine apnoea, this wag performed during spontaneous respiration under halothane drip anaesthesia. Intubation under Toxiferine relaxation would, of coui-se, also be possible. We did not, however, see any FREu ~ SEEGEI~: EXPERIENCE ~ITH TOXIFERINE 1'01 reason to change the mode of intubatlion x~chich is Usual" in our cli~ also for .didactic reasons. If there was sufficient spontaneous respiration at the end of the i operation (measured with a flow:meter and compared With 1)he values found before curariza- tion), the patient was extubated. If there were no.signsof residu~I curarization, that is, ,if the patient was able to open his eyes completely andi above all, to swaliow, decurarization was not necessary ,and ~therefore omitted. If there was some residual curarization, we first adminilstered atropine intravenolasly, then physostigmine* intravenously, and--aqcord,lng~ to~ degree of the remain.ifig curarization---perhaps pyridostigminet .(geinerally 1 rag. intramuscularly-and 1 rag. intravenously). If no signs of spontalneous respiration were detectable at all, at the end of the opegation (this occa~ionally.occ_urs in operation,s which, contrary to0 expectation, end as exploratorY, laparotomies) artificial reap!ration vas continued at any rate until, a meaSural~le, though low, spontanequs respi!Ta- tion could be detected and then only decurgrization was performed.

EXPERIMENTAL R~E S ULTS I~istarnine Effects (a) On the skin. Intravenous injection did not cause cutaneous sidle-effects in any of the ,volunteers; no exanthema~ous reactions which could have been the result of a hlstamme rerease ~ ere obs~rved~ In order to define possible histamine effects more exactly, we compared T0xiferine with other natural and synthetic non-depolarizing relaxants in the intracutaneous ti~st. We injected dilutions of Toxiferine and of d-tuboctrraiq,le, methylcurarine, gallamine, physiological saline, and histamine. The individual relaxants Were diluted according to their clilnical effectiveness, on the assumption that Toxiferine is 10 times, methylcurarineL ;3 times, and gallamin# 0.125 times as effective as d-tubocurarine. We investigated the substances in two different series 0f\dilutions; one contained .30 -y ToxiferiTae per injection, the other ;3 -y Toxiferine, and the coi-responding amounts of the other relaxants. The reactions were fully developed after 10 to 15 minutes andwore off in the course of the next hour or two. T he injection of ph~ysiological salinei caused, only a slight u-n~l~ecific red- dening. All tl~e relaxants caused more marked reddening and wheal, thi~ intensity being greatest With d-tubocurarine, medium with methylcurarine,' and ,leasVwith T0xiferine and_ gallamine. The two latter substances produced about equ.ally strong reactions. The duration of the reaqtions corresponded to their intensit:y;: the wheals and reddenings of the Toxiferine and gallamine injections wore off first, then those of methylcurarine, and lastly those of d-tubocurarine, Among the series Of weaker dilutions, a slight redden~n.g at the site of injection of d-tubo~ curarine could be observed after four hours. It, therefore, outlasted the effect of the injection of pure histamine. (b) On salivary secretion. In our auto,investigations, at least those with small doses, intravenous injection of Toxiferine caused no increase ir~ salivation, which *Prostigmin. tMestinon. 102 CANADIAN ANAESTHETISTS' SOCIETY IOURIQAL was marked only after d-tubocurarine. We cannot judgb the effect on salivary secretion of higher doses (23 3"/kg[ body-weight) becaus~ atropine was given as premedication in order to eliminate secretionas far as possible. These doses caused complete deglutition paralysis of 15 to 20 minutes duratibn, so that even normal salivary secretion would have increased the danger of asoira~,tion.

Effect on Blood Coagulation Knowing that d-tubocurars prolongs the-prothrombin and coagulation time- a property which is g~nerally considered to be due to heparin release, and because with clinical u~re of Toxiferine we had occasignally observed an unusual degree of parenchymatous haemorrhage during the op,pration, we also carried out prothrombin estimations (using the two-phase m'ethod) in some of our o/s+o, srag. Tb

0 * ! "/ " TO ,

I log "~ 90 ea ) D '& 80 sai zoo qs+u,sm, To --.+,rikg] 70 _~ I. Ta = 7-ox/Ferine PlC= Helhyl- curar/ne | "~< % ~ 7-o-----23~/ bodov-~'eA~'/7/ o,5+ z5. To I lmg --g3,v lk g

701 I I I I l ,GO E ;;r>/ " 0 1 23 4/ 5 fk -'0 1 2 3 1L/h. 0 / 2 3b, FIGURE 1. Changes in coagulation time in the hours following injection of Toxiferine: regu- lar prolongation of coagulation time. volunteers. The results varied considerably from test to test. Nevertheless, there was a regular fall in prothrombin which in some of the cases, however, especially at low doses, was only 5 to 10 per cent and, therefore, ha,d no significance. At higher doses, the reductions were generally more marked (from 10 to 20 per cent). In subsequent tests at the same dose (1 rag. = 23 -y/kg. body-weight) however, the prothrombin reduction varied from 5 to 23 per cent in one individual subject and a definite relationship could not, therefore, be determined. At a further increased dose of 1.5 rag. (fractionate injection of 1 and 0.5 rag.), there was a reduction of 35 per cent. A Corresponding slight prolon~gation of the coagulation time was occasionally observed. In contrast ~to d-tub0curarine with which the maximum effect on blood coagulation occurs a few miinutes after the injection, we observed the maximum effect of Toxiferine only after one to two hours. FREu ~ SEEGER: EXPERIENCE WITH TOXIFERINE 103 Our clinical observations also agree with this~ with i-laparotomy wehardly eyer saw increased haemorrhage when severing the sulbc, utaneous tissue and Lthe muscular layers, unless an increase in blood pressure had occurred beca~use the plarie of anaesthesia was too light at the beginning Of the Operation!; whereasjwe repeatedly observed increased haemorrhage f~om t~h~ mucosa in suturing anast- moses, for example, with gastrectomies, alth6ugh the circulation Was constant and the .blood pressure kept low. We should like to emphasize that such an i,ncreased haemorr~aagic tendency has been observed only in a small number of cases. One must take this difficqlty into account, however, and, in cas~s in which increased haemorrhage hin~lers the preparation or evokes additional dangers (for example, brain tumors, liver injuries, and so on), be more reluctant to giv~ large doses of relaxants. In operations of long duration" in which Toxiferine is indicated as'relaxant, the maximum of the coagulation disturbanc~ ocqurs during the course of the operation. In our opinion, there is no danger of increased secondary haem0~-rhage. None was observed in the cases we have treated t o date. Pulse Rate Changes in the pulse rate immediately after t~e injection of Toxiferine, and attributable to the relaxant, have not been observed in our investigations. At ~the peak of curarization, with marked restriction 6f .spontaneous respiratior~ or during artificial respira~:ion, there were, of course, especially in the first trials, occasional slight increases in the pulse rate (riot exceeding 100/rain.) which were of a psychogenic origin and humanly un~terstandable. In one volunteer ~vho underwent a total of 15 such tests, the initml pulse rate remained Un~changed for the whole duration of some of the later tests. Blood Pressure The same applies to the blood pressure values which were measured at i~ter- vals of one-half to two minutes. A significant fall in blood pressure following Toxiferine administration was never observed (i~3 contrast, there was a f~ll in blood pressure of 210 ram. systolic at times following even small doses of d- Tub0curarine Chloride and dimethyl-d-tubocurarjne). Occasionally, also at the peak of the curarization, there was a sl!~ght inc .t~ease in blood pressure (again due to psychogenic reasons and sometimes perhaps to a rise in the CO2 tension) with subsequent decrease to the norm or somew, h~tt below as the curare effect wore off. O~e The mode of action of Toxiferine is the classical curarelike one, that is, 'non- depolarizing. The course of the paralysis, therefore proceeds in the same m~nner and order as that due to d-tubocurarine. Toxiferine, however, is about 15 times more effective in the human than d-, as shown by com- parative studies of the two substances. (a) Effect on the ocular muscles. The influence on the Oculfir muscles iS the first to be felt and also lasts the longest. The sensitivity of th.e individual olcular muscles also varies (one can observe this best as the curare effecl~ wears off, ISince 104 CANADIAN ANAESTHETISTS' SOCIETY JOURNAL this takes place particularly slowly in the ocular muscles). From investigations with other non-depolarizing relaxant:s, it is known that the Mm. reciti interni are especially sensitive to curare. The same has been observed with regard to Toxiferlne: as the last objective symptom [!)efore the effect wore off, there re- mained a divergent strabismus even when tt~e patient was able to stand upright again. Only a very small amount of T0xiferine is apparently necessary to pro- duce this paralysis: after intragenous in, jection of only 0.25 rag. Toxiferine (corresponding to 5.6 ~//'kg. body-weight) we were able to observe this effect, subjectively experienced as diplopia, wiIthou;t paralysis of the 54. levator palpe- brae. This was the smallest intravenous dose given in our tests and we are in- clined to assume that even smaller doses would tSroduce this paralysis. (This assumption is based on an observation made accidentally and involu,ntarily in= one of our histamine tests. We intended ect 30 y Toxiferine intracutaneously and, due to incorrect techniqde, we ap] .qy hit a small subcutaneous vessel. Within a few minutes the volunteer suffered from diplo~ia and strabismus. One has, however, to take into considerati0n that the same volunteer had received other relaxants in corresponding" intracuta~mous dosage,~so that this incipient curarization might be attributed to a samm, ation effect. Therefore, 30"y cannot be considered as a dose causing initial 'parallysis of the ocular muscles.) (b) "Head drop" dose. T, he "head drop" dose which is so important in the animal experiment is of no interest in the l~uman. In our investigations, "head drop" occurred at the reduction of the grid strength to 15-30 per cent of the norm. In other words, the "head drop" dos,~ approximately corresponds to that which-reduces the grip strength to 15-30 p(~r cent of the norm. (c) Inflt~ence on vital capacity and gr.ip st)~ength. With sufficiently high doses, the total skeletal musculature, including the peripheral musculature of the respiratory tract and the diaphragm, are paralysed during the further course.of the curarization. Ill our tests, the effect on the respiration, measured by the vital capacity, and the reduction of the grip strength followed a paral!lel course, in that both decreased in a linear maturer to the-minimum which was reached within five minutes, on the average. In figlures, however, the reductionl of the vital capacity was markedly less than that cff the grip strength. A dose (17 y/kg. bod~.;-weight) which reduced the grip strength to about 40 per cent of the norm, reduced the vital capacity only to about 70, per cent of the initial vall'ue. An in- creased dose (23 ~//kg. body-weight), which lowered the grip strengtlh to 0 per cent, still left a vital capacity of 30 per cent. This difference must be attributed to a reduced sensitivity of the diaphra~gm because the remaining periphel-al muscu- lature of the respiratory tract as well as the slceletal muscles were iparalysed. W'here a sufficient spontaneous respiration and a relatively high vital capacity remai-ne.d, there was pure diaphragmatic respiration. ~h respect to the relationship between the reduction 6f the grip strength and~he reduction o'f the vital capacity, Toxiferine corresponds to d-tubocurarine, whereas the effect of methylcurarine* on the vital capacity was even lower: the dose of 0.1 mg./kg, body-weight, for insl~a, nce, reduced the grip strength to 0 per cent; the vital capacity, however, on!y to 60 per cent (in agreement with Sadove's results). Dmmth 9 yl-d- t ubocurario oe chloride. FREY & SEEGER: [EXPERIENCE =WITH TOXIFERINE] m5 Whereas, at the onset of action, the vital capacity and the grip strength uniformly decrease, with the wearing off of the effect, the vital capacity N. normalized more rapidly than the grip strength. Aftei- injection of ,1 mr. = 23 ~/kg. Toxifer.ine, for instance, the grip strength was still less than 5 per cent at the time when the vital capacity had again reached 50 per cent. At the time when the vital capacity was at 80 per cent, the grip s~re~gth was only 20 per cent; in other words, 50 per cent of the vital capacity was reached after 17 minutes, 50 per cent of the grip strength only after 38 minutes. The effect of this substance on the grip strength therefore lasted *wice as long as that on the vital capacity. The relatively prolonged influence on the grip strength is even more marked when Toxiferineis injected more slowly; especially in this respect there were marked differences in the effect in relationship to the speed of injec- tion (see Figs. 2 and 3). With rapid injection, normalization of the grip strength and.vital capacity is achieved more slowly than with slow injection. With raplcl injection, however, the prolongation of the action on the grip strength was more marked than. that on the vital capdcitS:.

Ruration of Action More than with other shorter-acting relaxants, the duration, of action of T0xgerine depended on the dose administered. In addition, as mentioned before, it depends to some extent on the spee d of the injection. When increasing intravenous d[oses of Toxiferine (0.25 rag., 0.5 rag.-, 0.75 mg., 1 rag.) were administered to a vdlunteer weighing 44 kg., restriction "of i:he ~ital capacity below 70 per cent of the norm and of the grip strength, belo w 40 'per -cent of the norm was found to be present for the following periods:

Duration of action

Vital capacity below Gri D strengeh below Dose 70 per cent of the 40 per cent of ehe norm norm

0.25 mr. --- 5.6 3,/kg. 0.5 mr. = 11 -r/kg. 7 min. 8rain. 0.75 mr. = 17 y/kg. 12 mln. 18 min. 1.0 m.g. = 23 7/kg. 26 rain. 37 rain.

Vital capacity and grip strength had returned-to normal after the fdjlowing lengths of time: 0.25 mr. = 5.6 ~,/kg. in 9 min. and 12 min. ; 0.5 mr. = g.l ~/kg. in15 min. and about 20 rain. ; 0.75 mr. ---- 17 "r/kg. in 20 min. and about 50 rain. ; 1.0 rng. -= 23 -r/kg. in 60 min. and about 60 rain. The duration of "head drop" after 23 ~/kg. was 16-17 min. depending on the rapidity of injection; the durat{on of deglutition paralysis was 15-20 min. after the same dose. A marked effect on the ocular muscles was observable for two hours. After this period, the volunteers were generally able to stand up and to walk--though somewhat unsteadily on the level floor. Minor after-effects such as unsteadiness in "climbing stairs, incapacity to read for long because of slight 106 CANADIAN ANAESTHETIST-N' SOCIETY JOURNAL

I i i 1 f i I 'f i'i -i I i I I ; I i J t % l~gTox/'fer/ne=23"~/hgbodj/-we/~7/7/ ]I I00 in ~Osec in 6"O inSsee in SOsN ...... -X Io i? ./+ .....o.=._.or..,~ ...... I ...~z__2../---~ 80 f ..'" / /" ,,-" //- ***" ,ff. o.-"l*~ / 6"0 I1" ,.'.+/ I/" ..'i'l / ":J~'/ (/0 .-!:..7/d/j/ ..';'/" io <.....-.>, Effi.ocf on gr? st/-eng/k 20

0 i r , ~ , L r I0 20 30 #0 50 zo 80'~ln w t:~-IGU R E 2. Effect of 1 rag. Toxiferine on grip-s~vength (summary of the results of 4 trials).

1 ~9 Tox/ferine=23 7/kg bo@- we/jTh/ /00~ %; ' ' ' ' in 90 seo 2~ "2"-~ _._.--.--~:..~, 00 .•//".l~g 5.....~"/77 3Osec /')~" 1..... I f**"

6"0 i i , i, / f ....S..~.,~* z *

# _ t~ Z f .L - .. j~+.~i ..~**

Ef,,~cfon v//a/capacil, v

'0~ I I I ], , I '] I ] I I 1 10 20 30 #0 50 mifl 60t~ i FIGURE 3- Effect of 1 rag. Toxiferine on the vital capacity (summary of the reslults of 4 trials). FREY (~ SEEGER: EXPERIENCE ~,V1TFI TOXTFER!INE 107 weakness in the ocular muscles, increased fatigability fgllow~ing repeated rapid movements could be Observed even five hours after the injection. In obese persons, the same dose per kg. body-weight prod~uced more marked L effects of somewhat longer duration. This is in agreeme?nt with the fact known from experience with other curare preparations that thedose of ,~ relaxant has to be reduced in the obese as well as fo~ persons who are (~onsiderably under- weight.

Accumulation (a) With repeated Toxiferine administration. One of the most impressive properties of Toxiferine is its marked propert.y of accumulation following repeated injections. Although this was to be expected be'cause of the long duration of action of this substance and the slow excretion, known from animal experiments, we were repeatedly surprised at the extent of this accumulation. In the first instance, we assessed these properties by subsequent injections of small doses of Toxiferine at short intervals of 15-20 min. compared with equiva- . lent doses .of d-tubocurarine and methylcurarine "(see Figs. 4 and 5). A very

0 15 30rain "I " J J "~=-'--7, 7- I I 1 I I II-'T-

I Pox/s I-rox, e Tox/ r/,,Z,y. or o.zs ro.-- 0.25r~g 4 000 - \ \each/n 5seconds" ~ ~,

3000 -

Vita/ capaci~- W ....

2 nO0 - Volunteer Dr..gee. #q k.g NO premed~ca/ion RR -120 RR .. " I o00 -- -- ' '

~ ~.. ..,~

- ~0 - :~ r" "Gripslrenglh ..- \of O- i I ', i _~ i i ', I ~ i i 70 0 10 20 30 90 60 SO mln FIGURE 4. Cumulative effeci~ of repeated intr~ven0us ipjections of 0.25 nag. Toxiferine~ I 108 CANADIAN ANAESTH]gTIS'IiS *, SOCIETY JOURNAL

I ] I I I II I I F I I d- tubOcur qrin e $ 2.Smg ! 2.Sptg 2.Stag r - in Ssec ~ i/zj.'sec /~ Ysec

15rnin ISrn/n

3000- V/'t#i cWr y

ff frulenlklo.'eer :Or. : dee.i8 3 Gor162 2000 - m e g/c a t/o n ." 0.5 mcl alrop/ne oro//j/ ~-50min

R# --120 Rg 1000-

...... -.~%~ ..... , % .~--.."'~"~'ulse" ...../: "-~/ 4:0 "" ""~ - _ ~rl~o strenjlk .... _1.~ I" _

s 1o o 1o 2S 3o ~a i, so mi~ FIGURE 5. Cumulative effect of repeated injections of 2.5 rag. d-tubocurarine in the same volunteer "-as in Figure 4. marked accumulation with regard to vital capacity and grip strength resulted from the administration of Toxiferine. Repeated doses of d-tubocurariine likewise produced these effects though they ~ ere liess pronounced. ,Methylct~Lrarine pro- duced almost no accumulation with regard to vital capacity, which+orresponds to its generally minor effect on the respiration, whereas a certain adcumulation With regard to grip strength was observed. The differences between the individual relaxants were not as marked when the intervals between the individual injec- tions were short. (b) Combination with other relaxants. For this purpose, we changed the experi- mental conditions in such a manner that ~,e allowed two hours to pass after the initial injection of 1 rag. = :23 %/kg. uritil,, apart from the above mentioned slight after-effects such as easy fatigabiHtv of the musculature, nq, subjective F-REY (Y~ SEEGER: EXPERIENCE Yr TOXIFER][NE 1-09 cura~re effects were felt (objectively, these had worn off earlier)i. We subsequently injected 89rng. Toxiferine (that is, half the initial dose) in a first test, 2 rag. methylcurarine in a control test (that is, the dose which, as sin~][e dose in the same volunteer, had decreased the vital capacity to 90 p~r ce,rlt of the norm and the grip strength to 60 per cent~, and 22 mg. succinylcholine in a third test (the full relaxant dose calculated for this subject). The results are shown in the Figures 6, Z, gtnd 8. A seyond injection of 89mg. Toxiferine two hours after the injection of 1 nag. Toxiferi,ne produced an equally strong and even longer lasting effect on the'~vltal ca.gacity and grip strength than the injection of 1 rag. Toxiferine given two hours earlier. Although the Mngle 'dose of dimethyl-d-tubocurarine hardly made any impression on l~he volunteer, the effects of this second injection on the respiration were not the minor ones otherwise typical of methylcurarine: on the contrary, the respiratory impairment was in this case so strong that artificial respiration had to be performed for-tefi minutes. This had not been necessary with the injection of Toxiferine alone. The resul:ts prove that two hours after the injection of Toxiferine, a great part of this relaxant, at least half of the dose administered, must still be present and active. In contrast to this, the subsequentr of s~ccinylcholine two hours after Toxiferine administration had a rf0rmal effect: nO cumulative effect was to be anticipated because this is a relaxant of the depolarizing type. However, there was no reduction of the effect. The muscle pains ,.which appeared ~fter the injection were also the same as those occurring after a single injection of succinylcholine. (c) Combination with anaesthetics. The inkenslty and duration of the effect of the individual Toxiferine doses mentioned above apply to injections in conscious v01un-teers who apart from small amounts of atropine adrninisiered with the highest doses of Toxiferinc had received no pretreatment. In any case, there is an additive effect on iJlae muscle relaxation produced by Toxif.erine during anaesthesia, and with some anaesthetics (for example, ether and halothane), a potentiating effect, with regard to both the intensity and above all the duration of the effect.

Side-Effects No side-effects whatsoever have been observed in any of our tests with Toxi- ferine, neither irritation of the wall of the vein associated with pain at the site of injection nor any general complaints. A certain feeling of giddiness which occasionally appeared at the beginning of tl~e paralysis also occurs witlT paralysis 0f the ocular muscle due to other causes, and disappeared when the volunteer closed his eyes. W'e have never observed exanthematous skin reacl ions, increased salivation, or changes in blood pressure or pulse rate.

Possibility of Being Antagonized Toxiferine, as other non-depolarizing relaxants, can be antagonized by cholin- esterase inhibitors. In our tests, we did not make use of this possibility as we were anxious to observe the~wearing off of the effect. We shall revert to this problem when discussing the clinical use of Toxiferine. l-1Oxl/ePine-._---, , , -l--7{1XIfer;ne Test#0."8;io.lf)(J

-·-----~----If7jeclioflOSmg IJr:See.9'¥k,g IJOfJO + fmg !imeJosec---:..------+' Po/(jn/eer

i HeodIJl'ojJ I I (allcur(}reeffecfs ~ / ,. !leadOrop I subjecliVely \ WOfIJ off)

JOOO-- ~~CI~

'"""fremeo'icoli{)!I.~'

,~:~~~~t:,op-2~:O~f/~ 2000- RR 16'0

i .. ~ /lR i ./11<\.. . ,., nnn Ii/Uil

flW~;;k~~ oo •• -., oooo - oo __ m - __ oon n m ... • _. .0 . ..·-lI- a_g"" e • .. _·e- __ •• .... ,_·_·_~·_·_)1_·_·_·-!l'-'-·_·-1__ W-, '\ 'tu/se ' -- If0 ley''''' .....1l~·Al-.-ll-Cr!jJslrf!!J!!/h I '\--- f-. _._._It''''- 0, f-...... / ....~ -...... __ ~"".1 . . ( '__ t_+- __ t...-e:---r' -- +_-t. t-i"",...... ~------_._---r--:------+:1 ..,.Jf'~.(jII+-~+ I 1\ . II ~_.- It Ill' ___ li'\.I~~_>il";"" o Illlolli~)f~''1-. II I IIIIII ~ "1,- I I I: .: I ! i I I IOmin0 10 20 JO '10 50 6'0 78 /80 ',10 100 110'110 1JO NO 150' 160 17f) 180rnin

{4;\,,uIi"OIIOIl,tl?lfgn, 100yflgOSjJOSffl

';FIGUHE,.6. Cumulative eff~ctof 0.5 mg. ToxiferillElldven two hours after f,mg!·:To~iferineinthesamevo!unteer, lmg Toxifef'il7eifI"5sec ~2~9Ivfetir/-;ur~ri;eI "'lesf#0.1016.J '1000 in sec WJ/{/!7teer/Jr.'See.'14kg I' ' .-.t 5 !leadJ),op . I I lIeud/)rofJ

3000 fremerlicfJ!io!l: /7/06mgafropine tHo!CUjJoci(r / or{l/(y' x -lh / t O-lSmg{llrojJlfle 2001}l- O((J!!r ~-IjfI ., f(f( 160 ------1000' .~"" --;r------~,.ffi-A-U~~W~_l

Qfl \ "'f;i;;>.~~~~~-;::~;;;;;;~."':O';;::.::':C::'~'~'--;:il.'~;7i;;;;;-"'"-.--.-'_A

...-x-~ .if \ '<.,~---U'7,I/FS , ~y Y '/ resn/f'fltIOfl ._. • ,'1.."" '~r ,.x- O'I"j I tJ ;;1;;,J.x,!x:

i--: i I ~ "'l''ii I i! i i i [ i i { { i I II I f O00- ~-'F-- i Tox ~ l :erln I ]e I Succinyld/cbol/ne ;'rag/n SO_sec 2Zrrt9 /n .qOsec rl..-,.i //Z? Head &op

3000 Test No l3 22 3 G0

-4 Volunteer Dr. See. ~/q k9 l)rern e dlc a/ion. 1 0.Srrt9 ~r/i-op/ne oral/f" Z000 ,z'- 7Gmtn RR L 7b'O

"000 ! I

l ...... "" k Pc,/se - qo k, CF/,o slre,~ih -"

"7-~ ' L--~-."-- ' -- i ~ T t ~ I r r r , i 1~, 2" t CiO 0 10 20 30 410 50 GO 70 80 90 ;00 ;;0 120 )'3O Z40 rn ffl FIGURE 8. Absence of cumulative effect of :22 mg. succinylcholine given,two hours after 1 rag. Toxiferfne in the same volunteer.

CLINICAL RESIULTS Histamine Effects As in the tests, we did not observe histamine effects with the clinical use of Toxiferine. Laryngospasm, bronchospasm, oi" other manifestations which might be attributed to histamine release never occurred, although we intentionally exclud~eeb.antihistaminics from the pretreatment of cases chosen for Toxiferine admiflistr~tion.

Pulse Rat~ and Blood Pressure

~Vi~h regard to the effects oil circulatio erine administrationI under ana/esghesia also confirms the results obta:ne~ ],n volunteers. There I were 110 9 9 i effects on circulation which could have been atf:ributed to Toxlferme. In the majority of cases, anaesthesia was maintained with halothane. In th4se, there was occasionally a falI in blood pressure and pulse rate following complete relaxa- tion and some minutes after respiration was controlled, especially if~this wa~ performed as a single phase direct pressure respiration. This effect is fhe result of the rapid flow of halothane and not of the muscle relaxant. Such fan effect was never observed when subsequent doses of Toxiferine were injecte'd during the course of the operation. Even ~nore ~clearly than these observatfions, the results of our auto-investigations confirm thai: Toxiferine has no such effect on the circulation. FREY ~s SEEGER: EXPERIENCE WITH TOXIFERINE 113 Clinical Dosage In order to achieve strong relaxation for protracted operations, we generally injected 2 mg. Toxiferine at the. beginning of the opegation .In ca.chectic or con- siderably underweight patients, we redtlced the dose Ito 1- L.6 mg. In almost all the cases, comp.ete1 paralysis of spontaneous respiration~ ~as a,zhieved within obe and a half to two minutes with these doses, of at least such a restriction of the ~espirfftion that it could easily be controlled. I!f, in very muscular men, respi~ratory paralysis was not achieved with 2 rag., a maxi/i lum of a further 89to 1 rag. was immediately injected. Only in occasional cases a,ere 3 mg. required,

ltyperi'nsullm'sm - ,?eqection oY P~ncreo~

s zooa 9 iTo ] roxiNrme Basal anaesthesia 500r~g ~]2mg~] 0.5rag We~h);" 8z.Z~g _ NzO n i $ 4 Ether ~rug: Thlbpentoi #aMhane ~ 0.5~ 1--0.5 t ~"~.5"-~ Amount: 500rrt 9 ];'me: 9.10 .. Ef/'ect. ~ood Fluid ~'dmi'n /str alio n : 5% levulose ,foo ~ L

4,\\\ , \,\\ \\ ., ,.,). . " ,f-- 2 _.- _: 200 (Rloqer ~s solutionr .. 8loud 1000 r~ ,Du.."~O.mallrespL~u.t/om, I60 5% levulose) Y50~ ?'lu~'/~ re,,'axo//o.~ffood, Pecu,~rJ/'tzJt,'o,q not reuui)"ed ~ o~ o.,z ~ /OF Der//o~?eo," Su./m:r'e

i 1 80'--

4U QMV: 5.q[ 9.5 9.5 qO.O 8.8 8.5 7.3 q.5 .G.8~

ResPim rl Pressure " i-z#'~.Cm l i 9 I i i ~ i ,; o ,1o 12 Is tlaemorrhaffe Cr Cr Cr C, C+ FIGURE 9. Anaesthetic data sheet showing long-lasting relaxation with Toxiferine in an opera- tion for pancreatic tumor.

and never more. The duration of adequate muscle relaxation (to fulfill even the highest d~mands) after single injection of the aforementioned dose was 46 to 130 min. When increase of muscle tension or reappearance of sp~ontaneous respira- tion began to interfere with.the operation, we administered ~ither 89rag. T~oxi- refine or 1 to 2 rag. methylcurarine if the operation was still expec~_ed to continue for some time, and this provided further relaxation for a good hour, or in soCme cases even longer. There is no contraindication to the additional administration 114 CANADIAN A N>k.ESTHETISTS' SOCIETY JOURNAL

Relaxant ~s#cci~liOOmt] .lbxlPer/ne roxirerine .Helhyl-cumnne Basalanaeslhesia 7 8arbi/umle ~00~ ~ 2rag , " ~ 7mg I N,~ l I 9 '[ Drug: Thiopenla/~ ttalotka~ ...... ~ l 0.5 1~0.s q , J Amoun/." fOOrn~ Hakrodex ]-/?he: 8. 25 Fluid admires/ration." 300,mL EFFect:flood

2oo (Rmyer"ssolu//on§ ...... -iT-"'" ' '~ " ' " ICO l . 5%levulose) IOOrrLL -- o4uraL o/ooa eocn

~0'

absorber ~aernorr~a~e1 Pleura open open ~mnchu.r dosed FIGURE 10. The anaesthetic data sheet showing ~omblned use of Toxlferine and other relaxants for difficult lobectomy. of succinylcholine for a short-lasting relaxatic)n which may be necessary after the Toxiferi'ne effect has completely disappeared. In our auto-investigations it has been proved that this is possible without danger. We wish, howe~v,er, to 9 = ] point out that it is generally impossible to await the complete fading of the Toxiferine effect during the operation. In such cases, we occasionally observed i that succinylcholine had an insufficient effect, or that relatively high doses were required in order to achieve the necessary relaxation. This might result in difficulties at the end of the operation, if the spontaneous respiration does not recur immediately and it cannot easily beldetermined to what extent the paralysis is due to Toxiferine and to v at extent to succinylcholine. Although no serious consequences result from this--at most, the patient mu~t receive artificial respiration after the end of the operation--we tend to fol)bw the repolarizing relaxant Toxiferine by a mnall dose of the likewise repolarizing relaxant methyl- curarine if a second injection is necessary. In this case, we are certain Iof being able to reverse the effect 9Or, if only a short-lasting relaxation is required, we prefer to inject only the amount of succinvlcholine generally required for a sufficient relaxation. If this dose is ineffective, relaxation should not be f6rced.by higher doses of succinylcholine. If worse comes to worse, one can try ir~creasing the depth of anaesthesia. For the maintenance of the anaesthesia, the aforementioned doses lvith tjae- addition of a small amount of halothane (we generally administered onllz 0.5 per cent and never exceeded 1-ger 9 cent) had a longer and more even effect~ tha"I1 -oxygen alone 9There seems to be a true potentiation. The possibilit3: of easy hyperventilation typical of hal~)thane anaesthesia is a particularly favourable feature as the effect of Toxif~rine wears off and often a~oids the necessity of a secdnd injection. FREY & SEEGER: EXPERIENCE WITH ~OXIEERINE 115 Possibihty oJ Being ~=Tntagonized I I decurarization is required, the following technique has proved t~ be appro- pri~te: if only a slight residual curanzatmn. . remains . on tl,ae, i . return of sufficient spontaneous respiration, t~e patient not yet being able to open his eyes com- pletely and having difficfllty ein swallowing, intravenous injection o,f 89rag. physostigmine following the administration of ~ to 1 nag. atropine will t rapidly abolish these slight residual effects. I n case of more prc~nounced residua ! curariza- ti0n, we gave an additional 89mg. physostigmin or /5 nag, pyridostigmi'n intra- muscularly. If sufficient spontaneous respiration had not been re-establishe~ at the end of the operation, we administered 1 mg. physo.'~tigmin intravenously following the intravenous injection of 89nag. atropine. At our Toxiferine dosa~ge, higher doses were never required to re-establish norm M spontaneous rest~iration. In order to avoid recurarization which might be expected because of the relatively sb0rt-lasting effect of physostigmin, when compared with the. duration of the effect of Toxiferine, we additionally administered 2.5 nag. pyridostigmin intra- ~.enously and 2.5 mg. intramuscularly. Vv'ith this procedure we r~ever observed recurarization. However, we always awaited the return of spontaneous respira- ti0n, even if only to a slight extent, before decurarization was performed.

.4cc~dents .or Deaths To date, we have not observed any accidents or deaths Which could have been attributed to the use of Toxiferine.

DISCUSSION AND CONCL17SIONS Indications (a) Operations of long duration. Because of its intensive and prolonged effective- hess, Toxiferine has proved t~ be excellent for protracted operations requiring strong, long-lasting, even muscle relaxation. In these cases Toxiferine can be used as the sole relaxant. Because it has no histaminic effects, there are no c0ntra-indications to its use in allergic or asthmatic patients. For operations of unpredictable duration, Toxiferine can be used in low dosage as the basic relaxant atad, if necessary, its effect increased by methylcurarhae or another repolarizing relaxant. (b) Tetanus. It so happened (it was, in fact,, a happy coincidlence) that at the time when Toxiferine was at our disposal we had only such mild cases of tetanus th~gno curarization was necessary at all. Thus, to date, we have had no oppor- tunity to use Toxiferine in cases of tetanus, but we are tzonvinced that it would be especially appropriate for such cases. (c) ~Veu'~ological and rheumatic diseases. Its even and long-lasting effect also justifies the attempt to use Toxiferine (subcutaneously in doses of 0.5 rag. to 1 mg.) in spastic diseases and contractures in the neurological field, as well as in rheumatic diseases, although, of course, in correspondingly lower dosage and under the supervision of an anaesthetist or physician who is experienced in the technique of intubation and artificial res.pirafion. 116 CANADIAN ANAESTt-IET~ISTS' SOCIETY JOURNAL Cont r a i nd icat io n s (a) Short operations. As shown by our tests, the duration of the effect of T0xl- ferine depends to a considerable extent on the dose. Toxiferine in lower dosage. could, therefore, also be used for shqrter operations. There is, however, on point in this. For short interventions there: are quite a number of very good short-acting relaxants which are easier (o handle. (b) Myasthenia gravis. Myasthenia gravis pseudoparalytica .represents a true contraindieation for any use of curare and therefore all the more for Toxiferine. (c) Disturbances of electrolyte and acetylcho,~,inesterase metabolism. As nle~ntior~ed before, we are somewhat more reluctant to administer Toxiferine in cases With impaired liver function or in cases in which there is a tendency t 9 haemorrh~ge from the very beginning or in which an increased parenchymatoUs haemorrhage might considerably disturb the operation. In severe disturbances of electrol.)te and acetylcholinesterase metabolism, it is oreferable to avoid the use of powerful and long-lasting relaxants.

SD'M,~][AR Y The iCalabash alkaloid Toxiferine is the most potent and long-acting relaxant of the curare group available to the clinic. As little as 2 mg. produces sufficient relaxation for all operative interventions in adults, of a marked "degree for~30 minutes and slowly wearing off during the next 30 minutes. As shown in 30 auto-investigations and 100 clinical cases, the drug is appr0, priate for muscle relaxation during operations of more than one hour duration. In addition, it is of value as a "basic relaxant"~ because it can be atatagonized by Prostigmin and can be combined with other relaxants. Only minor side-effects were observed: there was no marked histamine release L or pronounced effect on blood pressure and pulse rate. There were no accidents or deaths among our cases. Further clinical investigations of T0xiferine are justified, especially for 10ng- lasting relaxation in eases of tetanus arid neurological disease. Contraindicati0ns are: short-lasting operations; myasthenia gravis pseudoparalytica; disturbances of electrolyte and acetylcholinesterase metabolism.

Rt~SUM~ Les relaxants musculaires qui existent actuellement n'apportent~ pas encore tou.te satisfaction ~ l'anesthOsiologiste en ce qui concerne la durkee de-leur action, la possibilit~ d'Otre inhib6 par un antagoniste, et l'absence d'e~fets seconda[res. C'est pourquoi il est justifi5 de poursuivre les recherches en vue de mettre au point de nouveaux relaxants. L'isolement de la substance pure et la d~,termination de la structure chim!que des alcalo~des les plus importants extrm,ts du Calabash-curare, par P. Karrer et H. Sehmid, en 1958, ont 6veill6 le d6sir d'exp6rimenter la Toxif6rine au point de rue clinique. Les premiers ess.ais pharmacologiques et diniques ont 6t6 r6alis6s par ~vVaser et Harby. Au cours de nos recherches, la Tox{f6rine s'est av6r~e, par rapport h d'autres relaxants non-d6polarisants, ne i~rovoquer qffe de FREY r SEEGER" EXPERIENCE WITH TOXIFERINE 117- minimes effets secondaires de type'histaminique. Le pouls et la T.A. ne sont pas n0tablement modifi6s par des doses cliniques. L'ac,~ion est plus marqu6e et plus prolong~e que celle des a!caloides naturels du curare co:nnus jusqu'gt pr6sent. Chez l'adulte, il suffit d'une dose de 2 mg pour produire une relaxation durant de 40 ~ 120 minutes, qui'-permet toutes les interventions. Chez le sujet conscient et bien portant, une dose de 1 mg entraine une dmnnut..mn 9 9 ]o moyenne de ! 50% de la capacit6 vitale et jusqu'~ 10% de la force musculai~e. La d6pression de la capacit6 vitale est d'une dur6e t'r~s nettement plus br~ve (environ 20~minutes) que la diminution de la force de prehension (environ 40 minutes). Les sujets du sexe f6minin et les d6bilit6s r~pondent tt des doses ne d(}oassant oas 0,7 mg, de la maniSre pr~c6demment d6crite. Cliniquement, ce m6dicament s'est av6r~ eliicace dans plus de 100 anesth6sies pratiqu6es par les auteurs. I1 est indiqu6 comme relaxant (6ventuellement c0mme relaxant de base) dans les interventions chirurgicales devant durer plu- sieurs he.ures. I1 n'a pas 6t(} n6cessaire de d6passer l'a dose de 3 mg, la plus 61ev6e qui ait 6t6 utilis6e jusqu'5, pr6sent, car la r~p6tition des injections produit une v~ritable accumulation. On a 6galement constat6 que ,la T oxif6rine pouvait ~tre associ~e ~ la tub0curarine, & la dim~thyl-d-tubocttrarine, A la gaIlamine, etc., de m~me qu'~t l'Halothane, si la concentration de ce dernier ne d6passait pas 0;5% de l'air destin~ gt tetre inspir6. Toutefois des ~tud~s plus approfondies paraissent n6cessaires dans les cas d'interventions chirurgicales majeures de 10ngue dur~e requ~rant une relaxation prolongSe (dans les cas de t~tanus gravissime par exemple).

REFERENCES 1. BERLAG, F.; BERNAUER, K.; X'ON PHIL1PSBORN, W.; WASER, P.; SCHMIO, H.; & KARRER, P. Helvet. chim. ~Acta 42:394 (1959). 2. BERNAIdER, K.; BERLAGE, F.; YON PmLIVSBOR.~, W.; SCHMID, H. r KARRER,'P. l~lber die Konstitution der Calebassen-Alkalolde aus Strychnos toxifera. Helvet. chim. Acta 41: 2293 (1958). 3. FRE~', R. Vergleichende Untersuchungen der muskelerschlaffenden Mittel. Der Anaestheslst I': 11 (1952). 4. FRE~', R. Ergebnisse der Chirurgie und Orthoplidie 38:286 (1953). 5. FREY, R. Vergleichende Untersuchungen der Wirkungen muskelerschlaffender Mittel auf ', das Atemzentrum. Der Anaesthesist I: 3:3 (1952). 6. FREY, R. Die Muskelrelaxantien. In Frey, H0gin, & 5Mayrhofer, Lehrbl~h der Anaesthesio- logie. Heidelberg: Springer (lg55). 7. SI~.BECK, R., & FRE'Z, R. Die Wirkung muske..lerschlaffender Mittel auf :die Augenmuskeln. Der Anaesthesist 2:138 (1953). 8. WASER, P., & H~gBECK, P. Erste klinische Anwendung der Calebassenalkaloide. Der Anaes- thesist 8:193 (1959).