Abstract
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 1/75th 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 1/95th as much atropin was required; for eight times about 1/125th; and for sixteen times about 1/200th.
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 antagonize 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.
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