Promethazine, scopolamine and cinnarizine: comparative time course of psychological performance effects.

Single oral doses of promethazine (12.5 mg, 25 mg), scopolamine (0.6 mg), and cinnarizine (30 mg), were compared in a double-blind, placebo controlled trial. Twelve normal volunteers undertook a battery of psychological performance tests and a feeling state questionnaire, before drug administration, and at 2-h intervals after. Promethazine and cinnarizine significantly impaired psychomotor performance, information processing and feelings of alertness. With promethazine these reductions were maximal 3-4 h post-drug, with performance returning near to baseline 8-9 h post-drug. With cinnarizine these impairments were maximal 5-6 h post-drug, and performance remained depressed 8-9 h post-drug. Scopolamine significantly reduced feelings of alertness, and memory task performance; the overall performance effects were most evident 1-4 h post-drug.