Prescription ·Strong evidence ·Reviewed May 2026
Phenelzine is an irreversible nonselective MAOI used for depression, especially atypical or treatment-resistant depression when other antidepressants are inadequate. It can be highly effective but requires strict attention to tyramine-restricted diet, drug washouts, blood pressure, and serotonin-syndrome risk. Because it is a hydrazine MAOI, functional vitamin B6 depletion and neuropathy are clinically relevant safety issues.
The bottom line
Evidence rating strong. Most-documented uses: treatment-resistant major depressive disorder, atypical depression with hypersomnia or rejection sensitivity, some anxiety-spectrum symptoms when prescribed by specialists. 3 sources indexed (1994–2018), with 5 interaction records on file.
Core mechanism
Phenelzine irreversibly inhibits monoamine oxidase A and B, reducing metabolism of serotonin, norepinephrine, dopamine, and dietary tyramine. Increased synaptic monoamines mediate antidepressant effects, while impaired tyramine metabolism can trigger abrupt norepinephrine release and hypertensive crisis. Phenelzine can also interfere with pyridoxal-5-phosphate metabolism, contributing to vitamin B6 depletion and neuropathy risk.2,3
May be taken with or without food. Patients must avoid high-tyramine foods and beverages during therapy and for 2 weeks after stopping.
Nutrients this medication can lower over time, and what to replace.
Phenelzine is a hydrazine derivative that can bind or inactivate pyridoxal-5-phosphate, reducing active vitamin B6 availability and impairing B6-dependent neurotransmitter metabolism.
Phenelzine is an irreversible MAOI that can sharply reduce tyramine breakdown. High-tyramine foods can then trigger sudden, severe blood-pressure elevation and hypertensive crisis.
Recommendation: Avoid high-tyramine foods while taking Phenelzine and continue the MAOI diet for the prescriber-recommended washout period after stopping.
5-HTP increases serotonin synthesis while Phenelzine reduces monoamine breakdown. Combining them can cause dangerous serotonergic excess and serotonin syndrome.
Recommendation: Do NOT combine 5-HTP with Phenelzine. Use only if the prescriber managing Phenelzine explicitly directs it and provides washout instructions.
L-Tryptophan feeds serotonin synthesis while Phenelzine reduces serotonin breakdown, increasing risk of serotonin syndrome.
Recommendation: Do NOT combine L-tryptophan with Phenelzine unless specifically directed and monitored by the prescriber managing Phenelzine.
St. John's Wort is serotonergic and is inappropriate with irreversible MAOIs.
Recommendation: Do not use with phenelzine.
Rhodiola may have stimulant and monoaminergic effects, which are risky during nonselective MAO inhibition.
Recommendation: Avoid rhodiola while taking phenelzine.
Numbered references. Citations throughout the page link here.
Review discusses tyramine mechanisms and practical risk mitigation for MAOI prescribing.
Clinical reports link phenelzine exposure with pyridoxine deficiency and neuropathic symptoms.
Labeling describes MAOI indications, contraindications, hypertensive crisis risk, and tyramine food restrictions.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
Use this with your stack
Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.
NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.
