Effect of a Single Dose of Dextromethorphan on Psychomotor Performance and Working Memory Capacity

BACKGROUND: Previous studies show that the prolonged use of dextromethorphan produces cognitive deterioration in humans. AIM: The aim of this study was to investigate the effect of a single dose of dextroemthrophan on psychomotor performance and working memory capacity. MATERIALS AND METHODS: This is a randomized, double-blind, controlled, and prospective study. Thirty-six (17 women, 19 men) medical students enrolled in the study; half of them (7 women, 11 men) were given placebo, while the other half (10 women, 8 men) received dextromethorphan. The choice reaction time, critical flicker fusion threshold, and N-back working memory task were measured before and after 2 h of taking the drugs. RESULTS: Dextromethorphan showed a significant deterioration in the 3-back working memory task (P<0.05). No significant changes were seen as regards the choice reaction time components (total, recognition, motor) and critical flicker fusion threshold (P>0.05). On the other hand, placebo showed no significant changes as regards the choice reaction time, critical flicker fusion threshold, and N-back working memory task (P>0.05). CONCLUSION: A single dose of dextromethorphan has no effect on attention and arousal but may significantly impair the working memory capacity.