Phenelzine and 5-HTP / L-tryptophan

Desk tier: Avoid together

Mechanism: MAOI × serotonergic (serotonin syndrome / hypertensive crisis)

“patients being treated with NARDIL should not take sympathomimetic drugs … or related compounds (including methyldopa, L-dopa, L-tryptophan, L-tyrosine, and phenylalanine)”

Nardil (phenelzine), section CONTRAINDICATIONS. DailyMed label

Why this grade

Nardil (phenelzine) label, Contraindications

The Nardil (phenelzine) label lists this combination under Contraindications. CONTRAINDICATIONS: "patients being treated with NARDIL should not take sympathomimetic drugs … or related compounds (including methyldopa, L-dopa, L-tryptophan, L-tyrosine, and phenylalanine)" Named in the label: "L-tryptophan" Retrieved from DailyMed 2026-10-19.

Nardil (phenelzine) label on DailyMed

FDA boxed / safety communication

MAOI labels contraindicate serotonergic agents. Serotonin toxicity, hypertensive crisis.

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PMID 12925718

2003 QJM. Dunkley. Clonus, hyperreflexia, hyperthermia. The teaching screen.

PMID 12925718 on PubMed

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Educational reference only. Not FDA-cleared. The Prescribing Information governs.

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