CriticalSynthetic opioid, full mu-receptor agonist×Antidepressant, irreversible non-selective monoamine oxidase inhibitor (MAO-A and MAO-B)
Updated · Methodology
Mechanism
Methadone is an opioid with serotonergic activity and QT prolongation. Combined with phenelzine causes serotonin syndrome and additive QT effect.
Symptoms
Hyperthermia, myoclonus, respiratory depression, QT prolongation.
Management
Combination contraindicated. For OST in an MAOI patient, switch methadone to buprenorphine (less serotonergic).
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Nardil (phenelzine sulfate) prescribing information (2009)– FDA Nardil label, Section 4 Contraindications; DailyMed setid 513a41d0-37d4-4355-8a6d-a2c643bce6fa
- AEMPS: Ficha técnica: Metadona (nº registro 62423), sección 4.5 (2026)– AEMPS, CIMA, nº registro 62423, sección 4.5