Class Ia antiarrhythmic (sodium channel blocker with intermediate kinetics)
ATC code: C01BA01 (Quinidine)
Brand names
Quinaglute, Quinidex
Blocks cardiomyocyte fast sodium channels (phase 0 of the action potential) with intermediate binding kinetics. Also blocks IKr potassium channels, prolonging repolarisation (QT). Reduces sinus node automaticity and atrial, ventricular and His-Purkinje conduction. Strong CYP2D6 inhibitor, CYP3A4 substrate. Use in modern cardiology is restricted due to narrow therapeutic index and high proarrhythmic risk.
Third line
Quinidine is a third-line antiarrhythmic for atrial fibrillation when amiodarone and dronedarone are contraindicated or ineffective. 2024 explicitly moves quinidine to a reserve role because of sudden cardiac death risk, QT prolongation and torsades de pointes. Baseline renal and hepatic function, QTc, potassium and magnesium are required. ECG monitoring on days 1, 3 and 7.
6 pairs found. Sorted from critical to minor.
Mechanism
Dual QT prolongation (amiodarone extends 30–50 ms, quinidine 20–40 ms) plus amiodarone inhibits CYP3A4 (quinidine metabolism). contraindication.
Symptoms
QTc above 500 ms, syncope, torsades de pointes.
Management
Combination contraindicated. Choose one antiarrhythmic – usually amiodarone in severe AF.
Sources
Mechanism
Cobicistat inhibits CYP3A4 (quinidine metabolism) and itself prolongs PR via MATE1 inhibition. Quinidine concentration rises, additive QT effect.
Symptoms
QT prolongation, torsades de pointes.
Management
Combination contraindicated.
Mechanism
Quinidine inhibits renal and intestinal P-glycoprotein – digoxin clearance drops 50%. Concentration doubles with digoxin toxicity risk (bradycardia, AV block, ventricular arrhythmias).
Symptoms
Nausea, vomiting, visual disturbances, bradycardia, AV block within 5–7 days.
Management
Reduce digoxin by 50% when starting quinidine. Check level on day 5.
Sources
Mechanism
Quinidine is a strong CYP2D6 inhibitor (secondary pimozide pathway) and itself a QT prolonger. Double torsades risk. Orap Section 4.
Symptoms
QT prolongation by day 3, syncope, torsades de pointes.
Management
Combination contraindicated. If antiarrhythmic is needed in a pimozide patient, discuss catheter ablation or rate control with a beta-blocker without QT effect.
Mechanism
Additive QT prolongation (sotalol extends 30 ms, quinidine 20–40 ms). Torsades de pointes.
Symptoms
Syncope, torsades de pointes.
Management
Combination contraindicated.
Sources
Mechanism
Quinidine is a strong CYP2D6 inhibitor; flecainide is a CYP2D6 substrate. Flecainide doubles with proarrhythmic risk. BNF Appendix 1.
Symptoms
QRS widening, ventricular arrhythmias.
Management
Avoid combination. If quinidine is needed, reduce flecainide by 50%, ECG monitoring.
Sources
Opens the checker prefilled with this drug. Pick the second one from your regimen.
Pregnancy experience is limited but accumulated reports do not show major malformations. AEMPS allows use only when alternatives are unavailable.
Passes into breast milk in small amounts. Breastfeeding is possible with infant monitoring for arrhythmia signs.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Quinidine is evaluated for the following indications with varying evidence strength: Atrial fibrillation (evidence tier C). See the full indication matrix with dosing and citations above on this page.
Common side effects of Quinidine (≥ 1 in 100): Nausea, Diarrhoea, Cinchonism (tinnitus, dizziness), QT prolongation, Fatigue, Rash. See the Safety section for uncommon and serious reactions.
FDA category C. Pregnancy experience is limited but accumulated reports do not show major malformations. AEMPS allows use only when alternatives are unavailable.
Passes into breast milk in small amounts. Breastfeeding is possible with infant monitoring for arrhythmia signs.
Quinidine is contraindicated in: Combination with dronedarone, amiodarone, sotalol, dofetilide, flecainide – additive QT prolongation; Combination with usual-dose digoxin – digoxin toxicity via P-gp inhibition; Second- or third-degree AV block without pacemaker; Severe bradycardia (sick sinus syndrome); Prior thrombocytopenic purpura from quinidine or quinine. Full list in the Safety section.