OBSERVATIONS ON THE PHARMACOLOGY OF DIPHENIDOL, A POTENT ANTIEMETIC

¹ Department of Neurology and Cardiology, Smith Kline and French Laboratories, Philadelphia, Pennsylvania

Pharmacologic actions of diphenidol (, -diphenyl-1-piperidinebutanol, SK&F 478) and chlorpromazine were compared in animals. Although both drugs protect dogs against apomorphine-induced emesis, diphenidol does not depress motor activity at antiemetic doses and has a greater separation between the antiapomorphine ED50 and doses producing overt effects. In rats, unlike chlorpromazine, diphenidol neither blocks the conditioned escape response nor prolongs the duration of ether-induced prostration. Diphenidol is less potent than chlorpromazine in depressing motor activity of mice and in prolonging the duration of pentobarbital-induced prostration in rats. Diphenidol has no significant antihistamine activity in guinea pigs and does not alter the rate at which charcoal passes through rat intestine. In unanesthetized dogs, at oral doses 6 times the antiapomorphine ED50, diphenidol has no significant effect upon blood pressure, heart rate, respiration rate and electrocardiogram. In anesthetized dogs at intravenous doses up to 10 times the oral antiapomorphine ED50, diphenidol produces weak anticholinergic effects in the order of 1/330 the potency of atropine. The animal tests show that diphenidol is equal in antiapomorphine potency to chlorpromazine and that diphenidol has a greater selectivity of pharmacologic action. Clinical tests show good correlation with the laboratory observations and demonstrate that diphenidol is indeed an effective antiemetic agent in man.