Dextromethorphan and quinidine and Phenelzine interaction
Dextromethorphan and quinidine and Phenelzine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Phenelzine (phenelzine sulfate) label · effective 2026-05-21
Phenelzine sulfate should not be used in combination with dextromethorphan or with CNS depressants such as alcohol and certain narcotics.
OTC 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.
Patients should be warned that the use of the above foods, beverages, or medications may cause a reaction characterized by headache and other serious symptoms due to a rise in blood pressure, with the exception of dextromethorphan which may cause reactions similar to those seen with meperidine.
Also, there has been a report of an interaction between phenelzine sulfate and dextromethorphan (ingested as a lozenge) causing drowsiness and bizarre behavior.
From the Dextromethorphan and quinidine (Nuedexta) label · effective 2026-01-22
Use with an MAOI or within 14 days of stopping an MAOI.
Allow 14 days after stopping NUEDEXTA before starting an MAOI.
MAOIs NUEDEXTA is contraindicated in patients taking monoamine oxidase inhibitors (MAOIs) or in patients who have taken MAOIs within the preceding 14 days, due to the risk of serious and possibly fatal drug interactions, including serotonin syndrome.
Allow at least 14 days after stopping NUEDEXTA before starting an MAOI [ see Drug Interactions ( 7.1 ) ] .
Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.