Antagonism between Atropin and Central Emetics. 127 



7i ("35) 



Antagonism between atropin and certain central emetics. 



By Cary Eggleston. 



[Laboratory of Pharmacology, Cornell Medical College, New York 



City.] 



The minimal certainly emetic vein dose of pilocarpin alkaloid 

 (hydrochloride used) was determined for dogs as 0.7 mg. per kilo. 

 It having previously been observed that atropin was capable of 

 antagonizing the emetic action of pilocarpin, experiments were 

 made to determine the smallest dose of this alkaloid (sulphate 

 used) which was just sufficient to prevent emesis from the minimal 

 emetic dose of pilocarpin. The antagonistic dose of atropin 

 alkaloid was then determined for twice, four, eight and sixteen 

 times the minimal dose of pilocarpin. 



The results showed that it requires about i/75th as much 

 atropin base as of pilocarpin base to antagonize the emetic action 

 of the smallest effective dose of the latter. About the same ratio 

 was found for twice the dose of pilocarpin. For four times the 

 minimal dose of pilocarpin i/95th as much atropin was required; 

 for eight times about i/i25th; and for sixteen times about i/200th. 



Similar experiments were made with nicotin and atropin, but 

 the toxicity of the former drug prevented the use of amounts 

 larger than the minimal emetic dose. Atropin was found to an- 

 tagonize nicotin in the proportion of about 1 : 70 (both in terms 

 of base). 



Other emetics previously shown to cause vomiting through 

 central action were tested with atropin in doses up to 5.0 mg. of 

 the base per kilo, or 500 times the effective dose against pilocarpin 

 and 1,000 times that against nicotin. In no case was there any 

 antagonism demonstrable. The drugs used were apomorphin, 

 morphin, ouabain and emetin. 



It has been shown 1 that pilocarpin produces emesis through a 

 direct central action and since section of the vagi does not increase 

 the minimal emetic dose, a local action of the drug in producing 

 emesis seems very improbable. The antagonism of atropin, 



1 Eggleston, C. and Hatcher, R. A., Jour. Phartn. and Exp. Th.er., 1915, VII, 225. 



