Clinical effects of pentazocine in hospitalized medical patients.

Of 17,068 hospitalized medical patients monitored in a drug surveillance program, 616 (3.6 per cent) received pentazocine hydrochloride orally and 816 (4.8 per cent) received pentazocine lactate parenterally during one or more admissions. Unsatisfactory analgesic efficacy as judged by each patient's physician was nearly twice as frequent among recipients of pentazocine lactate as among recipients of parenteral morphine or meperidine. Adverse reactions were attributed to pentazocine hydrochloride in 18 recipients (2.9 per cent) and to pentazocine lactate in 37 recipients (4.5 per cent). Neuropsychiatric effects were the most common; they included hallucinations, bizarre feelings, disorientation, and agitation. These effects were dose dependent and frequently serious in nature. Minor gastro-intestinal effects were the second most common adverse reactions.