CriticalClass III antiarrhythmics (Vaughan Williams)×Class Ia antiarrhythmic (sodium channel blocker with intermediate kinetics)
Updated · Methodology
Mechanism
Dual QT prolongation (amiodarone extends 30–50 ms, quinidine 20–40 ms) plus amiodarone inhibits CYP3A4 (quinidine metabolism). FDA contraindication.
Symptoms
QTc above 500 ms, syncope, torsades de pointes.
Management
Combination contraindicated. Choose one antiarrhythmic – usually amiodarone in severe AF.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- DailyMed: Quinidine: FDA prescribing information, Drug Interactions section (DailyMed) (2024)
- AEMPS: Ficha técnica: Amiodarona (nº registro 81291), sección 4.5 (2022)– AEMPS, CIMA, nº registro 81291, revisión 06/2022, sección 4.5