The short answer
Review L-tryptophan with the prescriber before combining it with fluoxetine. The label warns about serotonin syndrome, while a small supervised trial also provides reassuring but limited evidence.
What this answer covers
Concentrated oral L-tryptophan, distinct from usual protein foods and L-5-HTP.
- Supplement or preparation
- L-Tryptophan
- Medication ingredient
- fluoxetine
Evidence includes a toxicity signal
An original five-case report is indexed for toxic reactions to fluoxetine plus L-tryptophan. Its full clinical details were unavailable, so it cannot supply a verified dose threshold or formal diagnostic count.
A small trial did not find serotonin syndrome
Thirty participants received fluoxetine with tryptophan or placebo for eight weeks. No serotonin syndrome occurred, but the higher tryptophan dose caused daytime drowsiness.
Do not turn trial doses into a recommendation
The trial’s early mood advantage did not persist at later assessments. Supervised research does not override the medicine warning or establish a supplement regimen for you.
Food and timing need separate interpretation
The concern is concentrated supplementation, not an instruction to avoid normal protein foods. Because fluoxetine and norfluoxetine persist, simply separating doses has no established protective effect.
Evidence and practical considerations
Side effects & toxicity
Conditional exact-label precaution with older toxic-reaction report and a small trial showing no serotonin syndrome both retained.
- Exact scope
- Concentrated oral L-tryptophan, distinct from usual protein foods and L-5-HTP. with Exact oral fluoxetine hydrochloride capsules. RxNorm IN 4493/PIN 227224 hydrochloride capsules. Active norfluoxetine and prolonged elimination matter. Not the combined olanzapine product.
- Medication form and route
- oral
- Timing or duration
- Source-specific single-dose, repeated-dose and observational exposures distinguished.
What remains uncertain
- Older report clinical details unavailable; trial too small to exclude rare toxicity or establish a universal safe dose.
Factors that may matter: preparation and plant part; clinical indication; dose; other medicines; baseline alertness.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed oral fluoxetine.
Exact label names tryptophan and St John’s wort in serotonin warnings, warns about bleeding and mania, and describes long elimination of fluoxetine and norfluoxetine.
How this applies: RxNorm IN 4493/PIN 227224 hydrochloride capsules. Active norfluoxetine and prolonged elimination matter. Not the combined olanzapine product.
No universal supplement interval, event rate or preparation equivalence established. Original label distinguishes warnings from measured pair-specific results.
Source 2: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Thirty people with major depressive disorder.
Early mood difference did not persist at later assessments. No serotonin syndrome reported; 4 g/day tryptophan caused daytime drowsiness.
How this applies: Only the named drug, preparation, route and measured endpoints apply.
Small supervised trial cannot exclude uncommon toxicity or establish an unsupervised dose recommendation.
Source 3: original case-report record
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Five cases identified in the original report title.
Original bibliographic record identifies toxic reactions with the combination.
How this applies: Only the named drug, preparation, route and measured endpoints apply.
No abstract; publisher route returned a redirect shell rather than clinical text. Exact symptoms, doses and formal serotonin-syndrome criteria not adjudicable from this capture.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Current exact available claims adjudicated using original captures and explicit identity and comparator limits. | |
| Research summary published |
Article revision: 62ded82460c8bc26
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.