Tranylcypromine isomers: single-dose effects in normal human subjects

Area of Science:

• Pharmacology
• Neuroscience
• Psychopharmacology

Background:

• Tranylcypromine is a monoamine oxidase inhibitor (MAOI) with chiral properties.
• Understanding the differential effects of its enantiomers is crucial for clinical application.
• Previous research has not fully elucidated the distinct psychophysiological impacts of (+)- and (-)-tranylcypromine.

Purpose of the Study:

• To compare the psychological and physiological effects of single doses of (+)- and (-)-tranylcypromine in healthy subjects.
• To investigate the influence of administration time (morning vs. evening) on the isomer-specific effects.
• To explore potential differences in subjective and objective measures between the two enantiomers.

Main Methods:

• Two double-blind, placebo-controlled experiments were conducted.
• Moderately high single doses of (+)- and (-)-tranylcypromine were administered to normal subjects.
• Psychological and physiological measures were assessed up to 24 hours post-administration.
• Effects were evaluated following both morning and evening dosing.

Main Results:

• Subjects consistently reported stronger subjective effects from the (+)-tranylcypromine isomer.
• Both active isomers induced sedative effects when administered in the morning.
• Evening administration of (-)-tranylcypromine led to delayed sleep onset.
• The (+)-tranylcypromine isomer, when given in the evening, was associated with an increased number of awakenings during the night.

Conclusions:

• The enantiomers of tranylcypromine exhibit distinct psychophysiological effects in humans.
• (+)-Tranylcypromine appears to have a more pronounced subjective impact and different sleep-disrupting properties compared to the (-)isomer.
• These findings suggest stereoselective mechanisms underlying tranylcypromine's actions and warrant further investigation into their clinical implications.