Brompheniramine, pseudoephedrine, and dextromethorphan and Phenelzine interaction
Brompheniramine, pseudoephedrine, and dextromethorphan 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.
The potentiation of sympathomimetic substances and related compounds by MAO inhibitors may result in hypertensive crises (see WARNINGS ).
Therefore, patients being treated with phenelzine sulfate should not take sympathomimetic drugs (including amphetamines, cocaine, methylphenidate, dopamine, epinephrine, and norepinephrine) or related compounds (including methyldopa, L-dopa, L-tryptophan, L-tyrosine, and phenylalanine).
Also, they should not be given cocaine or local anesthesia containing sympathomimetic vasoconstrictors.
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.
From the Brompheniramine, pseudoephedrine, and dextromethorphan (Brompheniramine Maleate, Pseudoephedrine Hydrochloride and Dextromethorphan Hydrobromide) label · effective 2026-01-13
Do not use dextromethorphan in patients receiving monoamine oxidase (MAOI) inhibitors ( see PRECAUTIONS – Drug Interactions ).
Drug Interactions Monoamine oxidase (MAO) inhibitors Hyperpyrexia, hypotension, and death have been reported coincident with the coadministration of MAO inhibitors and products containing dextromethorphan.
Concomitant administration of Brompheniramine Maleate, Pseudoephedrine Hydrochloride and Dextromethorphan Hydrobromide Oral Syrup and MAO inhibitors should be avoided ( see CONTRAINDICATIONS ).
In addition, MAO inhibitors prolong and intensify the anticholinergic (drying) effects of antihistamines and may enhance the effect of pseudoephedrine.
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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.