Definition The original antidepressants, phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine (Parnate) are all irreversible inhibitors of MAO-A and MAO-B, leading to pronounced effects on metabolism of endogenous (5-HT, NE, and DA) and exogenous (tyramine) monoamines. Selegeline is a selective MAO-B inhibitor – serotonin is deaminated by MAO-A (MAO-B primarily breaks down dopamine and phenethylamine), so the risk of serotonin […]