Dextromethorphan and quinidine and Propafenone interaction
Dextromethorphan and quinidine and Propafenone: 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 Propafenone (propafenone hydrochloride) label · effective 2026-01-29
Avoid the use of propafenone with Class IA and III antiarrhythmic agents (including quinidine and amiodarone).
Avoid concomitant use of propafenone and quinidine.
• Avoid use with other antiarrhythmic agents or drugs that prolong the QT interval.
Quinidine Small doses of quinidine completely inhibit the CYP2D6 hydroxylation metabolic pathway, making all patients, in effect, slow metabolizers [see Clinical Pharmacology ( 12.3 )] .
Concomitant administration of quinidine (50 mg 3 times daily) with 150 mg immediate-release propafenone 3 times daily decreased the clearance of propafenone by 60% in extensive metabolizers, making them poor metabolizers.
From the Dextromethorphan and quinidine (Nuedexta) label · effective 2026-01-22
Digoxin Quinidine is an inhibitor of P-glycoprotein.
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.