The effects of cimetidine and ranitidine on psychomotor function in healthy volunteers.

Single oral doses of cimetidine (400 mg), ranitidine (150 mg), promethazine (25 mg) or placebo were administered to 8 healthy volunteers in a double-blind study. Cimetidine and ranitidine did not cause any significant change in critical flicker frequency (c.f.f.), reaction time, pursuit rotor of the visual analogue scale scores for sedation. Promethazine significantly lowered c.f.f., prolonged reaction time and increased sedation when compared with placebo. It is concluded that in this study cimetidine and ranitidine had little, if any, effect on psychomotor function.