Effect of active metabolites of chlordiazepoxide and diazepam, alone or in combination with alcohol, on psychomotor skills related to driving.

Interaction of the main metabolites of diazepam and chlordiazepoxide with alcohol was measured in two subacute double-blind cross-over experiments on 40 healthy, young volunteers. The drugs were administered for two week periods. The variables measured were choice reaction time and accuracy, eye-hand co-ordination, divided attention, flicker fusion, proprioception and nystagmus. Chlordiazepoxide lactam, methyloxazepam and oxazepam significantly enhanced the alcohol-induced impairment of psychomotor skills, whereas N-desmethyl-diazepam did so only exceptionally in certain subjects in the choice reaction test. It is concluded that diazepam-alcohol interaction on psychomotor skills is mainly due to the parent compound. No correlation between the serum level of the agents and the changes in performance were found.