Tranylcypromine isomers: single-dose effects in normal human subjects.

Moderately high single doses of (+)- and (-)tranylcypromine were given to normal subjects, in the morning and evening, in two double-blind placebo-controlled experiments. Effects were determined up to 24h later by psychological and physiological measures. No significant differences were found on most measures, but the subjects consistently reported stronger effects after the (+)isomer. Both active drugs induced sedative effects when given in the morning. Following the evening administration, delayed sleep onset was reported after the (-)isomer, while the (+)isomer was associated with more awakenings during the night. The mechanisms responsible for these effects are discussed.