The effects of sulpiride on psychomotor performance and subjective tolerance

In many European countries, the substituted benzamide sulpiride is used with antidepressant indication in the dosage range of 150-300 mg on an outpatient population. This raises the concern of possible impairments of psychomotor performance in this dosage range. To address this question, the psychometric effects of 300 mg of sulpiride in comparison with placebo in 12 healthy volunteers was evaluated in this study. In a randomised, double-blind, two-way, within-subjects (cross-over) design, visuomotor performance was assessed using time estimation, critical flicker fusion, and choice reaction time tasks at baseline and 4 h after oral administration of either 300 mg of sulpiride or placebo. In addition, self-ratings on subjective well-being were obtained. Results were evaluated using analysis of covariance (ANCOVA) with baseline levels as covariates. In healthy subjects, 300 mg of sulpiride caused no alteration in time estimation and choice reaction movement time, whereas critical flicker fusion frequency was lower and choice-reaction decision time were prolonged under medication. Self-rating scales showed no significant differences between sulpiride and placebo. Subjects were not able to tell whether they received placebo or sulpiride. This study indicates that sulpiride is subjectively well tolerated at a dosage of 300 mg. However, using psychometric methods, effects are demonstrable that can be interpreted as a reduction of excitatory arousal without causing the subjective experience of sedation. These results call for caution when prescribing the drug to outpatients.