Diltiazem and Quinidine interaction
Diltiazem and Quinidine: the Quinidine prescribing label flags 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 Quinidine (Quinidine Gluconate) label · effective 2024-08-27
Proarrhythmic effects Like many other drugs (including all other Class Ia antiarrhythmics), quinidine prolongs the QT c interval, and this can lead to torsades de pointes , a life-threatening ventricular arrhythmia (see OVERDOSAGE ).
This hazard may be decreased if partial atrioventricular block is achieved prior to initiation of quinidine therapy, using conduction-reducing drugs such as digitalis, verapamil, diltiazem, or a β-receptor blocking agent.
Interactions with other dihydropyridine calcium channel blockers have not been reported, but these agents (including felodipine, nicardipine, and nimodipine ) are all dependent upon P450 IIIA4 for metabolism, so similar interactions with quinidine should be anticipated.
Drug and Diet Interactions Altered pharmacokinetics of quinidine: Diltiazem significantly decreases the clearance and increases the t 1/2 of quinidine, but quinidine does not alter the kinetics of diltiazem.
Non-interactions of quinidine with other drugs: Quinidine has no clinically significant effect on the pharmacokinetics of diltiazem, flecainide, mephenytoin, metoprolol, propafenone, propranolol, quinine, timolol, or tocainide .
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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.