Hypnotic efficacy of diphenhydramine, methapyrilene, and pentobarbital

The antihistamines diphenhydramine and methapyrilene were compared with pentobarbital for hypnotic effect in two Veterans Administration Hospital populations using subjective-response methods. In the first part of the study, 60 mg and 180 mg of pentobarbital were compared with 50 mg and 150 mg of diphenhydramine. A positive dose-response relationship was obtained only for pentobarbital; neither dose of diphenhydramine was significantly different from 60 mg of pentobarbital for any response variable. In the second part of the study, 100 mg of pentobarbital, 50 mg of diphenhydramine, and 50 mg of diphenhydramine, and 50 mg of methapyrilene were compared with placebo. One hundred mg of pentobarbital and 50 mg of diphenhydramine were significantly different from placebo, but 50 mg of methapyrilene was not.