TRANYLCYPROMINE

Clinical Use

Tranylcypromine is a nonhydrazine, irreversible MAO inhibitor antidepressant agent that was designed as the cyclopropyl analogue of amphetamine. Instead of exhibiting amphetamine-like stimulation, its mechanism of action is nonselective, irreversible inhibition of MAO. Its onset of antidepressant action is more rapid than for phenelzine. Tranylcypromine is well absorbed following oral administration. Metabolism occurs via aromatic ring hydroxylation and N-acetylation. It is a competitive inhibitor of CYP2C19 and CYP2D6 and a noncompetitive inhibitor of CYP 2C9. Most metabolism studies suggest that tranylcypromine is not metabolized to amphetamine contrary to debate. Maximal MAO inhibition, however, occurs within 5 to 10 days. The GI absorption of the tranylcypromine shows interindividual variation and may be biphasic in some individuals, achieving an initial peak within approximately 1 hour and a secondary peak within 2 to 3 hours. It has been suggested that this apparent biphasic absorption in some individuals may represent different absorption rates. Following discontinuance of tranylcypromine, the drug is excreted within 24 hours. On withdrawal of tranylcypromine, MAO activity is recovered in 3 to 5 days (possibly in up to 10 days). Concentrations of urinary tryptamine, an indicator of MAO-A inhibition return to normal, however, within 72 to 120 hours.