The short answer
Tryptophan supplements can increase the risk of serotonin syndrome with amphetamine sulfate. If co-use is necessary, the prescriber may need a lower stimulant starting dose and monitoring, especially when starting or increasing treatment. Do not adjust an existing dose yourself.
What this answer covers
Applies to concentrated L-tryptophan supplementation with systemic amphetamine sulfate; the record does not establish the same risk from ordinary dietary protein.
- Supplement or preparation
- L-Tryptophan
- Medication ingredient
- amphetamine sulfate
Evidence and practical considerations
Side effects & toxicity
Exact labeling explicitly lists tryptophan among serotonergic agents that can increase serotonin-syndrome risk.
- Exact scope
- tryptophan with amphetamine sulfate
- Medication form and route
- systemic amphetamine sulfate
- Timing or duration
- Risk is relevant during concentrated supplement co-use, especially initiation and titration.
What remains uncertain
Factors that may matter: tryptophan supplement dose; other serotonergic agents; amphetamine dose.
Read the supporting source summaries
Source 1: current United States prescribing information
dailymed.nlm.nih.gov · Source check Jul 25, 2026
Population: Patients prescribed oral amphetamine sulfate.
The serotonin-syndrome warning explicitly includes tryptophan; lower initiation and monitoring are advised if co-use is warranted.
Label describes agent categories and does not quantify a universal supplement dose, timing interval, or absolute risk.
Research assessment: · Open full citations ↗
Timing & monitoring
Exact labeling names tryptophan and provides lower-dose and monitoring instructions if co-use is warranted.
- Exact scope
- tryptophan with amphetamine sulfate
- Medication form and route
- systemic amphetamine sulfate
- Timing or duration
- During concentrated supplement co-use and particularly initiation or titration.
What remains uncertain
Factors that may matter: supplement dose; other serotonergic agents; amphetamine dose.
Read the supporting source summaries
Source 1: current United States prescribing information
dailymed.nlm.nih.gov · Source check Jul 25, 2026
Population: Patients prescribed oral amphetamine sulfate.
Tryptophan is included in the serotonergic-drug warning; lower initiation and monitoring are advised if co-use is warranted.
Label describes agent categories and does not quantify a universal supplement dose, timing interval, or absolute risk.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Research summary published |
Article revision: 43cedeb5de141553
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.