Actions and interactions of cinnarizine and phenylpropanolamine on human psychomotor performance

Abstract

This placebo-controlled, double-blind, crossover study was conducted to evaluate the actions and interactions of cinnarizine and a centrally acting sympathomimetic agent on human psychomotor performance. Twelve healthy men received single doses of 10 mg of cinnarizine (C), 50 mg of phenylpropanolamine (P50), the combinations of 10 mg of cinnarizine with 25 mg (CP25) or 50 mg (CP50) of phenylpropanolamine, and respective placebos, in balanced order at 1-week intervals. Digit symbol substitution, tapping, flicker fusion, tracking, choice reactions, and body balance tests were administered before drug intake (between 4 and 5 pm) and 1, 2, and 3 hours posttreatment. Two-way analysis of variance and paired t test were used to analyze the drug-induced changes from baseline. No significant drug-induced impairment of coordination or reaction skills were found. Compared with placebo, CP50 improved digit symbol substitution at 2 hours and impaired the flicker fusion threshold at 3 hours. The sagittal body sway was reduced by P50 (at 1 hour) and by CP50 (at 1 and 2 hours). We conclude that the mild sedation produced by cinnarizine is counteracted by the doses of the stimulant used. A potential therapeutic interaction of cinnarizine and phenylpropanolamine is likely.