The short answer
Avoid L-tryptophan supplements with phenelzine. The medication label explicitly warns against this combination and describes serious neurologic and behavioral reactions with MAOIs and tryptophan. An hours-apart schedule has not been shown to prevent the problem.
What this answer covers
Supplemental oral L-tryptophan with phenelzine tablets. This is not a blanket prohibition on normal protein-containing foods and does not substitute 5-HTP for tryptophan.
- Supplement or preparation
- L-Tryptophan
- Medication ingredient
- phenelzine
Why this is an avoidance warning
Tryptophan is a serotonin precursor, and phenelzine inhibits monoamine breakdown. The prescribing information specifically identifies tryptophan, so this is not just a broad warning based on the supplement category.
Describe the outcome accurately
The label describes confusion, agitation, incoordination, jerking and abnormal reflexes in MAOI-tryptophan reactions. Separate reports describe hypomania. These observations support concern but should not all be relabeled as the same diagnosed syndrome.
Food is a different question
This page addresses a tryptophan supplement, not avoidance of every ordinary protein food. Follow your existing MAOI food advice and ask the prescriber before adding a concentrated amino-acid product.
Do not manage this by hours apart
No protective spacing schedule was verified. A switch requires an individualized prescriber plan. New confusion, fever, rigidity or jerking after serotonergic products needs urgent medical assessment.
Evidence and practical considerations
Side effects & toxicity
NARDIL explicitly lists L-tryptophan and describes MAOI-tryptophan neurologic/behavioral syndromes. Published case abstracts also report hypomania; this outcome is kept distinct from confirmed serotonin syndrome.
- Exact scope
- Supplemental oral L-tryptophan with phenelzine tablets. This is not a blanket prohibition on normal protein-containing foods and does not substitute 5-HTP for tryptophan. with Oral phenelzine tablets; current sulfate-tablet labeling uses the named active ingredient.
- Medication form and route
- oral
What remains uncertain
- The inspected case abstract does not give each patient's exact MAOI regimen. Event frequency and an individual safe dose are not established.
Factors that may matter: Exact supplement preparation and complete concomitant-medication list require assessment..
Read the supporting source summaries
Source 1: Current U.S. prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral phenelzine sulfate tablets.
The label prohibits sympathomimetics, L-tryptophan, L-tyrosine, phenylalanine and serotonergic agents. It warns about excessive caffeine and high-tyramine exposures.
How this applies: Primary authority for phenelzine oral-tablet precautions; each article identifies whether the supplement is named or the application is a constituent/class inference.
Regulatory instructions do not quantify an exact-pair event rate or validate every botanical formulation.
Source 2: Human case reports
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Two patients receiving an MAOI; the abstract does not give per-patient medication and dose detail.
Hypomania followed addition of tryptophan.
How this applies: No original full text was available; indexing includes phenelzine and tranylcypromine but cannot be used to assign the exact regimen of each patient. Hypomania is not interchangeable with serotonin syndrome.
No original full text was available; indexing includes phenelzine and tranylcypromine but cannot be used to assign the exact regimen of each patient. Hypomania is not interchangeable with serotonin syndrome.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Initial targeted research draft. Inspected source material, adjudicated the current checker statements, and recorded preparation limits. Clinical review has not occurred. | |
| Research summary published |
Article revision: 2b997b84bd4e599f
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.