Phenelzine
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Missing image Phenelzine.png Chemical structure of phenelzine Phenelzine | |
| Phenethylhydrazine | |
| Empiric formula | C8H12N2 |
| Molecular weight | 139.19 |
| Bioavailability | ? |
| Metabolism | Liver |
| Elimination half life | 1.2 hours |
| Excretion | Urine |
| Pregnancy category | C (USA) B3 (Aus) |
| Delivery | Oral |
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Indicated for:
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Phenelzine is an antidepressant drug that belongs to the monoamine oxidase inhibitor class of drugs.
Mode of action
Phenelzine is a derivative of hydrazine, which is phenylethylamine-like moiety and similar to normal substrates of MAO. When MAO tries to oxidize phenelzine, this hydrazine-moiety binds covalently to the enzyme, thus inactivating it irreversibly. Phenelzine is a non-selective MAO-inhibitor, it inhibits both MAO-A and MAO-B.
Pharmacokinetics
Phenelzine is administered orally as phenelzine sulphate and it is rapidly absorbed form the gastro-intestinal tract. Although phenelzine has a fairly short half-life, its effect lasts for several, until new functional MAO-enzymes have been produced by the body. Phenelzine is acetylated in the liver and its metabolites are excreted in the urine.
Side effects
Common side effects include orthostatic hypotension, dizziness, headache, fatigue and gastro-intestinal disturbances. Phenelzine can cause, though rarely, severe hepatotoxicity, most likely due to its hydrazine group.
As with other MAOIs, tyramine-containing foods can cause a cheese reaction, which is a severe hypertensive crisis, so users of phenelzine must adhere to rigid dietary guidelines. This hypertensive crisis is characterised by severe headache and rapid rise in blood pressure, which can cause cardiac failure and intracranial hemorrhage.