Effect of mesoridazine administration and withdrawal on performance in an older age group.

Seven subjects, aged 48-62 years, took a placebo capsule nightly for 3 weeks, mesoridazine 10 mg for 3 weeks, and then placebo for 3 weeks. Mesoridazine is a short half-life phenothiazine useful as a hypnotic. Performance was assessed during three experimental sessions on each test day. In spite of subjective sleepiness 20 min after rising, psychomotor performance 1-3 h later was not imparied, except possibly manual dexterity after the first dose. Neither auditory vigilance, nor digit symbol substitution were affected noticeably by the drug at any time of day. Card sorting of varying degrees of complexity was unimpaired, though there was a suggestion that the drug might be associated with better performance on the most complex task.