Drug interactions
L-tryptophan + Phenelzine
Severity: Major
L-tryptophan and Phenelzine: major interaction.
Last updated
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 with an MAOI blocking serotonin breakdown, excess serotonin can accumulate. This can cause serotonin syndrome with agitation, hyperthermia, tremor and autonomic instability.
What this interaction means in plain words
L-tryptophan and Phenelzine 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 reduced serotonin metabolism through MAO inhibition.
What to do
Avoid the combination. If tryptophan was taken, stop it and monitor for serotonin toxicity.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for L-tryptophan and Phenelzine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Phenelzine
- 5-HTP + Phenelzine Contraindicated
- Amitriptyline + Phenelzine Contraindicated
- Amoxapine + Phenelzine Contraindicated
- Atomoxetine + Phenelzine Contraindicated
- Benzphetamine + Phenelzine Contraindicated
- Brimonidine + Phenelzine Contraindicated
Frequently asked questions
Can I take L-tryptophan with Phenelzine?
MediHelp rates the interaction as major. L-tryptophan and Phenelzine 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 with an MAOI blocking serotonin breakdown, excess serotonin can accumulate. This can cause serotonin syndrome with agitation, hyperthermia, tremor and autonomic instability.
How serious is the interaction between L-tryptophan and Phenelzine?
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 the combination. If tryptophan was taken, stop it and monitor for serotonin toxicity.
What other medicines interact with Phenelzine?
MediHelp also lists interactions of Phenelzine with, for example, 5-HTP, Amitriptyline, Amoxapine. The full list is on the Phenelzine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
