Dextromethorphan and quinidine and Methylene blue interaction
Dextromethorphan and quinidine and Methylene blue: 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 Methylene blue (PROVAYBLUE) label · effective 2025-05-28
Opioids and dextromethorphan may increase the risk of developing serotonin syndrome.
…including antidepressants like SSRIs (selective serotonin reuptake inhibitors), SNRIs (serotonin and norepinephrine reuptake inhibitors), MAOIs (monoamine oxidase inhibitors), bupropion, buspirone, clomipramine, mirtazapine, linezolid, opioids, and dextromethorphan because of the potential for serious CNS reactions, including potentially fatal serotonin syndrome.
Clinically significant drug interactions with PROVAYBLUE are described below: The concomitant use of PROVAYBLUE with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
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 ) ] .
MAOIs Do not use NUEDEXTA with monoamine oxidase inhibitors (MAOIs) or in patients who have taken MAOIs within the preceding 14 days [ see Contraindications ( 4.3 ) ] .
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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.