A study of the psychometric effects of chlormethiazole in healthy young and elderly subjects.

The pharmacokinetics and effects of chlormethiazole (91 mg intravenously together with 356 mg orally) on psychomotor performance were studied in 10 young (mean age 29 years) and 10 older (mean age 66.2 years) volunteers using an open design. Chlormethiazole affected psychomotor function and decreased subjective arousal in both age groups. The peak effect was found at approximately 30 min, i.e. at the end of the infusion, and performance returned to normal by 3 h. There was no evidence of increased sensitivity of the older subjects to the psychomotor or subjective effects of chlormethiazole. The incidence and type of reported symptoms was also similar in the two age groups. The volume of distribution of chlormethiazole was greater in the old than in the young subjects as was the elimination half-life after intravenous administration. Other pharmacokinetic variables showed no significant differences between young and old subjects.