Drug interactions
Fluoxetine + L-tryptophan
Severity: Major
Fluoxetine and L-tryptophan: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Tryptophan is a serotonin precursor, and giving it with an SSRI can overstimulate serotonin pathways. Cases of serotonin syndrome have been reported with this type of combination.
What this interaction means in plain words
Fluoxetine and L-tryptophan can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Increased serotonin synthesis from tryptophan combined with reuptake inhibition by fluoxetine.
What to do
Avoid routine use of tryptophan supplements with fluoxetine. If used, start with a low dose and monitor for agitation, tremor, diaphoresis, clonus and hyperthermia.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Fluoxetine
- Fluoxetine + Isocarboxazid Contraindicated
- Fluoxetine + Mavacamten Contraindicated
- Fluoxetine + Methylene blue Contraindicated
- Fluoxetine + Phenelzine Contraindicated
- Fluoxetine + Pimozide Contraindicated
- Fluoxetine + Rasagiline Contraindicated
Frequently asked questions
Can I take Fluoxetine with L-tryptophan?
MediHelp rates the interaction as major. Fluoxetine and L-tryptophan can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Tryptophan is a serotonin precursor, and giving it with an SSRI can overstimulate serotonin pathways. Cases of serotonin syndrome have been reported with this type of combination.
How serious is the interaction between Fluoxetine and L-tryptophan?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid routine use of tryptophan supplements with fluoxetine. If used, start with a low dose and monitor for agitation, tremor, diaphoresis, clonus and hyperthermia.
What other medicines interact with Fluoxetine?
MediHelp also lists interactions of Fluoxetine with, for example, Isocarboxazid, Mavacamten, Methylene blue. The full list is on the Fluoxetine page.
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