Quantitative comparison of the anticholinergic and antiarrhytmic actions of disopyramide and quinidine

With the purpose of estimating quantitative differences between disopyramide and quinidine two experimental series were designed. In order to establish the atropinic potency of both drugs, pA2 values were determined in rabbits right atria, using acetylcholine as agonist. The capacity to prevent ventricular fibrillation in albino mice subjected to chloroform apnea was also tested using various doses of the drugs. An effective median dose (ED50) to each of the drugs was calculated and the relative antiarrhythmic potency was compared. Disopyramide showed in both experimental series to be a more potent agent than quinidine.