Phenelzine is the least expensive ($43 monthly) and most prescribed of the oral MAOIs for depression, although prescriptions for any MAOI are rare due to risk of serotonin syndrome and hypertensive crisis. Dietary tyramine must be restricted, as shown in the isocarboxazid (Marplan) monograph on the preceding page.
Phenelzine inhibits MAO-A and MAO-B almost equally, with slight preference for MAO-A. It is metabolized to phenylethylamine (PEA), which produces effects similar to a short acting amphetamine.
“Does this phunnel make me look phat?”– Unlike the other MAOIs, phenelzine may cause weight gain.
Risk of mortality in single-drug overdose with MAOIs is similar to that of tricyclics. Of 392 single-drug exposures to phenelzine reported to Poison Control, there were 2 deaths (Nelson & Spyker, 2017).
Dosing: Start 15 mg TID and rapidly increase to 30 mg TID (which is the maximum dose of 90 mg/day) then decrease slowly over several weeks to the lowest effective dose. Use lower dose with elderly patients. Taper slowly to stop.