Cyclobenzaprine and Dextromethorphan and quinidine interaction
Cyclobenzaprine and Dextromethorphan and quinidine: 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 Cyclobenzaprine (TONMYA) label · effective 2026-08-14
If serotonin syndrome symptoms occur with the use of other serotonergic drugs, immediately discontinue TONMYA.
Other serotonergic Drugs: Serotonin syndrome has been reported ( 5.2 , 7 )
If concomitant treatment with TONMYA and other serotonergic drugs is clinically warranted, careful observation is advised, particularly during treatment initiation or dosage increases.
If concomitant treatment with TONMYA and other serotonergic drugs (besides MAO inhibitors) is clinically warranted, careful observation is advised, particularly during dosage increases.
From the Dextromethorphan and quinidine (Nuedexta) label · effective 2026-01-22
Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions.
Anticholinergic Effects of Q uinidine Monitor for worsening clinical condition in myasthenia gravis and other conditions that may be adversely affected by anticholinergic effects.
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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.