The short answer
Do not self-start L-5-HTP with amoxapine. Official L-5-HTP guidance advises against combining it with antidepressants, even though the exact pair’s clinical risk is not quantified.
What this answer covers
Concentrated oral L-5-hydroxytryptophan, not L-tryptophan or whole Griffonia seed.
- Supplement or preparation
- L-5-HTP
- Medication ingredient
- amoxapine
The supplement guidance is explicit
Health Canada advises not to use L-5-HTP with antidepressants. Amoxapine is an antidepressant, so that product precaution applies to a review decision.
Do not substitute another precursor
L-5-HTP and L-tryptophan are different substances. A whole seed preparation or mixed mood supplement may have a different and uncertain exposure.
A dose gap is not a clearance
Bring all mood products and amounts to the prescriber. No validated supplement spacing rule removes the warning.
Recognize a serious change
New high fever, marked muscle rigidity or confusion needs urgent assessment. Amoxapine has a neuroleptic malignant syndrome warning; these symptoms should not automatically be labeled a supplement-induced serotonin interaction.
Evidence and practical considerations
Side effects & toxicity
Conditional avoidance of unsupervised co-use follows explicit supplement guidance, not a documented exact-pair serotonin event.
- Exact scope
- Concentrated oral L-5-hydroxytryptophan, not L-tryptophan or whole Griffonia seed. with Exact oral amoxapine tablets. RxNorm IN722, exact oral amoxapine tablets. Active hydroxy metabolites and dopamine-receptor effects do not make it identical to other antidepressants or antipsychotics.
- Medication form and route
- oral
- Timing or duration
- Source-specific single-dose, repeated-dose and observational exposures distinguished.
What remains uncertain
- Amoxapine label does not explicitly name L-5-HTP or serotonin syndrome; no exact-pair clinical event established.
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 amoxapine.
Label describes a mild sedative component, dopamine-blocking and neuroleptic malignant syndrome concerns, and active metabolites. It does not explicitly name serotonin syndrome or the requested supplements.
How this applies: RxNorm IN722, exact oral amoxapine tablets. Active hydroxy metabolites and dopamine-receptor effects do not make it identical to other antidepressants or antipsychotics.
No universal supplement interval, event rate or preparation equivalence established.
Source 2: official product guidance
webprod.hc-sc.gc.ca · Source check Sep 10, 2026
Population: Adults considering oral L-5-HTP.
Advises not to use with antidepressants; gives serotonergic product precautions and drowsiness caution.
How this applies: The requested medicine is an antidepressant; this is a product-label precaution, not exact-pair clinical proof.
Does not quantify risk with each specific antidepressant or establish a safe supplement dose.
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: 1800549d09560917
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.