Combined effects of buspirone and diazepam on objective and subjective tests of performance in healthy volunteers

The combined effects on performance of two anxiolytics with different mechanisms of action were evaluated double-blind and crossover in 12 healthy students. Objective (tracking, divided attention, Maddox wing, etc.) and subjective (visual analogue scales and questionnaires) tests were done before and twice after single oral doses. Diazepam (0.15 and 0.30 mg/kg) impaired performance dose relatedly and rendered the subjects drowsy, calm, mentally slow, and clumsy. Buspirone (15 mg) proved inactive in objective tests but matched diazepam (0.30 mg/kg) subjectively. In combinations, buspirone added to the effects of diazepam in Maddox wing and letter cancellation but tended to counteract diazepam effects on divided attention and learning acquisition. Subjectively buspirone prolonged diazepam-induced sedation. Increased calmness caused by diazepam was not affected by concomitant buspirone. It is suggested that combining small doses of buspirone to diazepam does not cause any additional decrement in psychomotor performance. Possible advantages of the diazepam-buspirone combination in therapeutic use are discussed.