Psychomotor, physiological and cognitive effects of scopolamine and ephedrine in healthy man

Summary

Three placebo-controlled double-blind studies in healthy volunteers were performed to reveal the psychophysiological effects of scopolamine, ephedrine and their combination. Single intravenous dose of scopolamine 6 µg/kg (scopolamine hydrobromide 7.4 µg/kg) impaired various psychomotor functions both subjectively and objectively. It caused sedation, impairment of coordinative and reactive skills, visual disturbances and impairment of short-term memory. Oral scopolamine hydrobromide in single doses of 0.3 mg and 0.9 mg, or 0.9 mg b.d. for 3 days, had few effects. A slight impairment of short-term memory and a decrease in the flicker fusion threshold were seen. The visual nearpoint and pupil diameter were increased and some subjects reported blurred vision and dizziness during treatment with scopolamine 0.9 mg b.d. Scopolamine showed clear cardiovascular effects in all studies: it decreased heart rate and systolic blood pressure. Ephedrine alone and in combination with scopolamine had no deleterious effects. On the contrary, it antagonized the scopolamine-induced impairment in the flicker fusion test and the decrease in blood pressure and heart rate. In sufficient doses scopolamine impairs various psychomotor and cognitive skills. An oral dose of scopolamine hydrobromide 0.9 mg on average has few effects, although they may be very striking in certain individuals. To avoid unwanted effects and diminition in performance by scopolamine, doses less than 0.9 mg should be used.