Supplements and Phenelzine.
Phenelzine, sold under the brand name Nardil, is a monoamine oxidase inhibitor (MAOI): it irreversibly inhibits MAO-A and MAO-B, with strict dietary and drug interaction rules.
Phenelzine is a monoamine oxidase inhibitor (MAOI). The class irreversibly inhibits MAO-A and MAO-B, raising synaptic monoamine levels. Current UK use is uncommon. It is confined to depression that has resisted other treatments and is managed in specialist psychiatry, because of the strict dietary rules (foods rich in tyramine) and drug interaction rules. The supplement surface is one of the most restrictive in clinical pharmacology. Anything serotonergic stacked on top can drive serotonin syndrome. St John's Wort, 5-HTP, tryptophan, SAMe, rhodiola, and saffron extract are all excluded. Anything sympathomimetic stacks on noradrenergic effect. Caffeine at high doses, yohimbe, bitter orange, ephedra (where available), and even excessive ginseng warrant care. Supplements rich in tyramine and certain protein extracts carry the same hypertensive crisis concern as the dietary tyramine rule. The psychiatric team is the gatekeeper for any new supplement on an MAOI regimen.
Below are the 8 documented pairs we have explicitly assessed against Phenelzine in the Distil database: 7 severe and 1 caution. The pairs cluster around 2 mechanisms: MAOI pressor (blood-pressure surge) and Additive serotonergic activity. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 14 September 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
MAOI pressor (blood-pressure surge)
Severe Does L-Tyrosine interact with Phenelzine?
Taking L-Tyrosine with phenelzine (an irreversible MAOI) may push blood pressure up sharply, because tyrosine is the raw material your body turns into adrenaline and noradrenaline and the MAOI blocks their breakdown, so we treat this as a do-not-combine pair without specialist sign-off.
Evidence: No direct study of this exact combination yet; the caution rests on a plausible mechanism or on reports involving a related medicine.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Caution Does Panax Ginseng interact with Phenelzine?
There are a few old published case reports of an interaction between ginseng and the MAOI phenelzine. They are short letters and editorials with no abstract we can check, so we do not repeat the symptoms often quoted from them, and a later systematic review records only that the two may interact. The reason is not understood, but ginseng has mild stimulant-like effects on the nervous system that can clash with MAOIs. If you take phenelzine, do not start ginseng without talking to the doctor who manages your antidepressant.
Evidence: Limited human data, from small studies or case reports.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive serotonergic activity
Severe Does 5-HTP interact with Phenelzine?
5-HTP raises serotonin levels. Combined with an MAOI like phenelzine, which blocks serotonin breakdown, this can produce severe serotonin syndrome. Do not combine.
Evidence: Supported by human study data.
Severe Does L-Tryptophan interact with Phenelzine?
Tryptophan is the building block your body uses to make serotonin, and phenelzine is an MAOI that blocks serotonin breakdown. Combining them can drive serotonin to dangerous levels and has caused toxic reactions in published cases. Do not combine.
Evidence: Supported by human study data.
Severe Does Rhodiola Rosea interact with Phenelzine?
Rhodiola appears to slow the same enzyme (monoamine oxidase) that phenelzine blocks. Stacking the two could push serotonin and related signals too high, risking serotonin syndrome or a dangerous rise in blood pressure. We treat this as a do-not-combine pair without specialist sign-off.
Evidence: No direct study of this exact combination yet; the caution rests on a plausible mechanism or on reports involving a related medicine.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Severe Does SAMe interact with Phenelzine?
SAMe raises serotonin-related activity, and phenelzine is an MAOI that blocks serotonin breakdown. Stacking the two could push serotonin too high, risking serotonin syndrome. We treat this as a do-not-combine pair without specialist sign-off.
Evidence: No direct study of this exact combination yet; the caution rests on a plausible mechanism or on reports involving a related medicine.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Severe Does Saffron Extract interact with Phenelzine?
Saffron has its own antidepressant effect that appears to act on serotonin, and phenelzine is an MAOI that blocks serotonin breakdown. Stacking the two could push serotonin too high, risking serotonin syndrome. We treat this as a do-not-combine pair without specialist sign-off.
Evidence: No direct study of this exact combination yet; the caution rests on a plausible mechanism or on reports involving a related medicine.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Severe Does St John's Wort interact with Phenelzine?
St John's Wort with an MAOI like phenelzine can cause hypertensive crisis and serotonin syndrome. This is a strict do-not-combine.
Evidence: Supported by human study data.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How the checker decides
Every result has a source
Each pair we have assessed is cited to a published study (PMID) or the British National Formulary, so you can read the source yourself.
Four kinds of answer
Severe, caution, no known interaction, and not yet assessed. A pair we have not assessed is never shown as clear.
- Severe
- Caution
- No known interaction
- Not yet assessed
Nothing in our data is not a clearance
When nothing in our data records a problem with a pair, the result says no known interaction at typical doses, which is not a clearance: your pharmacist or GP can check the pair against your full medical history.
A full supplement review, built around you, not a generic stack.
The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
£49 until 30 June 2027 · £79 from 1 July 2027.
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