Irreversible, non-selective MAO inhibitor. The reference case for both hazards on this page.
Also known as: Nardil. Category: medication.
What it does, mechanism by mechanism
MAO-A inhibition — inhibits, strong
Blocks monoamine oxidase A, the enzyme that breaks down serotonin, noradrenaline and dietary tyramine. Two separate hazards come off one enzyme: serotonin accumulates (toxicity) and dietary tyramine is no longer destroyed in the gut wall (pressor response).
Irreversible; enzyme activity returns only as new enzyme is synthesised, over about two weeks.
Blocks monoamine oxidase B, which preferentially handles dopamine and phenylethylamine. At low, B-selective doses the tyramine hazard is much smaller; selectivity is lost as dose rises.
In patients receiving nonselective monoamine oxidase (MAO) inhibitors in combination with serotoninergic agents (e.g., dexfenfluramine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram, venlafaxine) there have been reports of serious, sometimes fatal, reactions. Because Phenelzine Sulfate Tablets is a monoamine oxidase (MAO) inhibitor, Phenelzine Sulfate Tablets should not be used concomitantly with a serotoninergic agent.
FDA Structured Product Labeling, retrieved via the openFDA drug/label API (CC0 1.0 Universal) on 2026-09-09.
A clean result means NO DOCUMENTED INTERACTION IN THIS DATASET. It does not mean safe, and it is not a clearance. Most substances are not in this dataset at all, and for many pairs that are, nobody has ever studied the combination.
Serotonergic drugs and the serotonin-toxicity mechanism
Dietary tyramine and L-dopa loads
The major cytochrome P450 pathways: CYP3A4, CYP2D6, CYP1A2, CYP2C9, CYP2C19 — inhibition and induction
P-glycoprotein inhibition and induction
11β-HSD2 inhibition (the licorice mechanism) and the potassium consequences that follow it
QT prolongation as an additive pharmacodynamic axis
Culinary seasonings and common foods with documented pharmacological activity
A selected set of narrow-therapeutic-index drugs where those shifts matter most
Not in this dataset
Any substance not named in this dataset — which is most substances. There are tens of thousands of marketed drugs and this table holds fewer than a hundred entries.
Phase-2 conjugation (UGT, SULT, NAT2, COMT) except where a specific entry names it. The oilahuasca corpus turns heavily on phase 2 and this engine models it only in passing.
Pharmacogenomics. CYP2D6 and CYP2C19 are strongly polymorphic; a poor metaboliser and an ultra-rapid metaboliser can have opposite outcomes from the same pair, and this engine does not know your genotype.
Dose, timing, duration, formulation and route — all of which change whether a documented interaction is clinically real for you.
Renal and hepatic impairment, age, pregnancy, and body composition.
Additive sedation, respiratory depression, bleeding risk, hypoglycaemia and most other pharmacodynamic axes beyond the ones listed above.
Herb–herb interactions outside the named entries, and essentially the whole botanical world: most plants have no interaction literature at all.
Allergy, intolerance, and contamination or adulteration of unregulated products.
Anything published after the last-reviewed date below.
72 substances, 20 mechanisms,
64 citations. Last reviewed .
Primary literature (every DOI resolved against the Crossref API) and FDA drug labelling. There is no free, openly-licensed, comprehensive drug-interaction dataset to draw on; NLM retired its Drug Interaction API on 2024-01-02 and DrugBank's interaction set is a commercial licence.
References
Gillman PK (2011). Advances Pertaining to the Pharmacology and Interactions of Irreversible Nonselective Monoamine Oxidase Inhibitors. Journal of Clinical Psychopharmacology. doi:10.1097/JCP.0b013e31820469ea
Gillman PK, Feinberg SS, Fochtmann LJ (2018). A reassessment of the safety profile of monoamine oxidase inhibitors: elucidating tired old tyramine myths. Journal of Neural Transmission. doi:10.1007/s00702-018-1932-y
Every DOI above was resolved against the Crossref API on 2026-09-09 and the returned
title checked against the one printed here. Three DOIs in the first draft resolved to real but different
papers and were corrected before publication.