What the FDA labels say about taking them together
Dextromethorphan and phenelzine
Phenelzine's FDA label of June 6, 2025 names dextromethorphan in its contraindications section; dextromethorphan's label does not name phenelzine itself but warns about its class (MAO inhibitors). The phenelzine label: “OTC Medications To Avoid Cold and cough preparations Nasal decongestants (tablets, drops, or spray) Hay-fever medications Sinus medications Asthma inhalant medications Antiappetite medicines Weight-reducing preparations …”
Check it at the source: the dextromethorphan FDA label on DailyMed (effective August 27, 2026); the phenelzine FDA label on DailyMed (effective June 6, 2025, Parke-Davis Div of Pfizer Inc).
What does the dextromethorphan label say about phenelzine?
Dextromethorphan's label does not name phenelzine itself; it warns about its class (MAO inhibitors):
Dextromethorphan label, warningsWarnings Do not use if you are now taking a prescription monoamine oxidase inhibitor (MAOI) (certain drugs for depression, psychiatric or emotional conditions, or Parkinson’s disease), or for 2 weeks after stopping the MAOI drug.
Dextromethorphan label, warningsIf you do not know if your prescription drug contains an MAOI, ask a doctor or pharmacist before taking this product.
Source: FDA drug label (Good Sense Cough DM), L. Perrigo Company, effective August 27, 2026 (SPL set 5a2e9bef-42cb-4b72-9a26-c3ae71dcb4ea), via openFDA; the full label on DailyMed
What does the phenelzine label say about dextromethorphan?
Phenelzine label, contraindicationsNARDIL should not be used in combination with dextromethorphan or with CNS depressants such as alcohol and certain narcotics.
Phenelzine label, warningsOTC Medications To Avoid Cold and cough preparations (including those containing dextromethorphan) Nasal decongestants (tablets, drops, or spray) Hay-fever medications Sinus medications Asthma inhalant medications Antiappetite medicines Weight-reducing preparations "Pep" pills L-tryptophan containing preparations Also, certain prescription drugs should be avoided.
Source: FDA drug label (Nardil), Parke-Davis Div of Pfizer Inc, effective June 6, 2025 (SPL set 513a41d0-37d4-4355-8a6d-a2c643bce6fa), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Dextromethorphan | Phenelzine | |
|---|---|---|
| Labeled for | Cough and cold | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.122 per unit 15 mg softgel | $0.586 per tablet 15 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once