Dextromethorphan and quinidine and Disopyramide interaction
Dextromethorphan and quinidine and Disopyramide: 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 Disopyramide (Norpace) label · effective 2026-08-24
Concomitant Antiarrhythmic Therapy The concomitant use of Norpace or Norpace CR with other Type 1A antiarrhythmic agents (such as quinidine or procainamide), Type 1C antiarrhythmics (such as encainide, flecainide or propafenone), and/or propranolol should be reserved for patients with life-threatening arrhythmias who are demonstrably unresponsive to single-agent…
Patients who have evidenced prolongation of the Q-T interval in response to quinidine may be at particular risk.
Concomitant administration of Norpace and quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels.
Other antiarrhythmic drugs (e.g., quinidine, procainamide, lidocaine, propranolol) have occasionally been used concurrently with Norpace.
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.