The effect of neuroleptics on cognitive and psychomotor function. A preliminary study in healthy volunteers.

The effects of haloperidol (1 mg), benzhexol (5 mg), diazepam (10 mg) and caffeine (400 mg) on subjective and objective measures of cognitive and psychomotor function were compared with placebo in 20 healthy volunteers. While both diazepam and benzhexol were associated with highly significant impairments in subjective altertness, critical flicker fusion threshold and choice reaction time (CRT), haloperidol could not be distinguished from placebo in most tests but was actually associated with an apparent improvement in CRT (in males) and simple visual reaction time. The perceptual maze test detected impairment by benzhexol on processing speed but was not sensitive to any other drug effects. Multiple-dose studies are required to establish if there is a true activating effect of haloperidol using a test of sustained attention. No effect of Eysenck personality subtype or life events on baseline or drug response data was detected.