Class Ia antiarrhythmic (sodium channel blocker with intermediate kinetics)
Brand names: Quinaglute, Quinidex
Updated · Methodology
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.
Sources
ICD-10: I48 · ICD-11: BC81.3
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.
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.
7 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.
Sources
Mechanism
Posaconazole strongly inhibits the liver enzyme CYP3A4 (posaconazole label), and the liver clears quinidine mainly through this enzyme (US quinidine label). As a result, posaconazole raises quinidine plasma levels, which prolongs the QT interval on the electrocardiogram and can cause torsade de pointes (posaconazole labels). Quinidine itself prolongs the QT interval in a dose-related way, and cases of torsade de pointes have been reported with posaconazole. The posaconazole label also lists quinidine among drugs that inhibit posaconazole clearance and may raise its levels. The documents give no numbers for this pair. The US quinidine label reports that quinidine levels rise with ketoconazole, another azole antifungal.
Symptoms
The main danger is QT interval prolongation on the electrocardiogram, torsade de pointes and other ventricular arrhythmias up to ventricular fibrillation (posaconazole and quinidine labels). The risk is higher with a slow heart rate, low potassium, magnesium or calcium and high quinidine levels, but the arrhythmia can occur without any of these (US quinidine label). Excess quinidine causes low blood pressure, vomiting, diarrhoea, tinnitus, hearing loss, vertigo, blurred or double vision, headache and confusion (US quinidine label). An arrhythmia attack shows as sudden strong palpitations, dizziness or fainting.
Management
The combination is contraindicated (posaconazole label, European Medicines Agency, ; posaconazole label, US Food and Drug Administration, ). Quinidine is named in the contraindications, including in the generic posaconazole label (Spanish Agency of Medicines and Medical Devices, AEMPS). The FDA posaconazole label contraindicates posaconazole with all drugs that are broken down by the enzyme CYP3A4 and prolong the QT interval. Use posaconazole with caution in people with a prolonged QT interval, cardiomyopathy (especially with heart failure), sinus bradycardia or existing symptomatic arrhythmias (posaconazole label, EMA). Check potassium, magnesium and calcium and correct them as needed before and during posaconazole treatment (posaconazole labels, EMA and FDA). The QT interval on the electrocardiogram is a better guide to quinidine safety than its blood level (quinidine label, FDA). In haemodynamically unstable torsade de pointes, stop quinidine and perform immediate cardioversion or overdrive pacing, and actively correct low potassium, magnesium and calcium (quinidine label, FDA).
Sources
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
Verbatim lines from the interaction sections, in the language of the label
«Medicamentos que inducen Torsades de pointes: Antiarrítmicos de la clase Ia, como quinidina, procainamida, disopiramida.»AEMPS, section 4.5 · Open on CIMA
«CONTRAINDICATIONS: Antiarrhythmics Amiodarone (with ritonavir), quinidine (with ritonavir)»FDA, section 4 · Open on DailyMed
«amiodarona, bepridilo, dronedarona, ivabradina, quinidina, ranolazina»AEMPS, section 4.3 · Open on CIMA
«Está contraindicada la administración de terfenadina a pacientes en tratamiento con dosis múltiples de 400 mg o superiores de fluconazol al día, en base a los resultados de un estudio de…»AEMPS, section 4.3 · Open on CIMA
«La administración conjunta de hidroxizina con fármacos que se sabe que prolongan el intervalo QT y/AEMPS, section 4.5 · Open on CIMA
«Pérdida auditiva: Se ha notificado una pérdida transitoria o permanente de la audición en pacientes tomando un tratamiento con itraconazol. Varias de estas notificaciones incluyen la administración…»AEMPS, section 4.4 · Open on CIMA
«Drug Interactions: Coadministration of a number of CYP3A4 substrates such as dofetilide, quinidine cisapride and pimozide is contraindicated with ketoconazole tablets. Coadministration with…»FDA, section 4 · Open on DailyMed
«Uso concominante con derivados de la quinidina (ver sección 4.5).»AEMPS, section 4.3 · Open on CIMA
«Fármacos que prolongan el intérvalo QT, p.ej., mizolastina, pimozida, quinidina, sertindol, terfenadina, astemizol, cisaprida, bepridil, dofetilida, halofantrina, ya que el incremento de las…»AEMPS, section 4.3 · Open on CIMA
«Está contraindicado el uso concomitante de fármacos que inhiben el CYP3A4, tales como antifúngicos azólicos, antivirales inhibidores de la proteasa , antibióticos macrólidos y nefazodona (Ver sección…»AEMPS, section 4.3 · Open on CIMA
«DRUG INTERACTIONS: Because pimozide prolongs the QT interval of the electrocardiogram, an additive effect on QT interval would be anticipated if administered with other drugs, such as phenothiazines…»FDA, section 7 · Open on DailyMed
«Administración concomitante con los sustratos del CYP3A4 terfenadina, astemizol, cisaprida, pimozida, halofantrina o quinidina, dado que esto puede causar un aumento en las concentraciones…»AEMPS, section 4.3 · Open on CIMA
«CONTRAINDICATIONS: • CYP3A4 substrates (pimozide, quinidine): can result in QTc interval prolongation and cases of torsades de pointes (TdP) ( 4.3 , 5.2 , 7.2 )»FDA, section 4 · Open on DailyMed
«Administración concomitante de antiarrítmicos de clase Ia (p.ej. quinidina) o clase III (p.ej. dofetilida, sotalol) distintos de la amiodarona.»AEMPS, section 4.3 · Open on CIMA
«Antiarrítmicos: La coadministración con ritonavir es probable que dé como resultado un aumento de las concentraciones pl asmáticas de amiodarona, bepridil, dronedarona, encainida, flecainida…»AEMPS, section 4.5 · Open on CIMA
«CONTRAINDICATIONS: Antiarrhythmics: amiodarone, dronedarone, flecainide, propafenone, quinidine»FDA, section 4 · Open on DailyMed
«Antiarrítmicos: Sotalol no debe combinarse con antiarrítmicos de clase Ia, como disopiramida, quinidina, procainamida y flecainida, ni con otros medicamentos antiarrítmicos de clase III como…»AEMPS, section 4.5 · Open on CIMA
«Quinidina»AEMPS, section 4.3 · Open on CIMA
«CONTRAINDICATIONS: Coadministration of pimozide, quinidine or ivabradine with voriconazole tablets is contraindicated because increased plasma concentrations of these drugs can lead to QT…»FDA, section 4 · Open on DailyMed
«CONTRAINDICATIONS: dofetilide, sotalol, quinidine, other Class Ia and III anti-arrhythmics, mesoridazine, thioridazine, chlorpromazine, droperidol, pimozide, sparfloxacin, gatifloxacin, moxifloxacin…»FDA, section 4 · Open on DailyMed
«DRUG INTERACTIONS: Antiarrhythmics quinidine, procainamide, flecainide Reserve concomitant use for patients who are unresponsive to a single agent. Antiarrhythmic metabolism inhibited by amiodarone…»FDA, section 7 · Open on DailyMed
«Los fármacos que prolongan el intervalo QT , incluidos antiarritímicos como la quinidina, los antihistamínicos astemizol y terfenadina, algunos antipsicóticos (particularmente la pimozida y el…»AEMPS, section 4.5 · Open on CIMA
«Drugs Having Clinically Important Interactions with Aripiprazole: Strong CYP3A4 Inhibitors (e.g., itraconazole, clarithromycin) or strong CYP2D6 inhibitors (e.g., quinidine, fluoxetine, paroxetine)…»FDA, section 7 · Open on DailyMed
«Antiarrítmicos de Clase-I (ej. quinidina, disopiramida; lidocaína, fenitoína; flecainida, propafenona): Pueden potenciar los efectos sobre el tiempo de conducción auriculoventricular y aumentar el…»AEMPS, section 4.5 · Open on CIMA
«DRUG INTERACTIONS: Disopyramide Quinidine Dofetilide Amiodarone Sotalol Procainamide Not Recommended Disopyramide, Quinidine: There have been postmarketing reports of torsades de pointes occurring…»FDA, section 7 · Open on DailyMed
«Established and Other Potentially Significant Drug Interactions: Cardiac Disorders : ranolazine, ivabradine dronedarone Other antiarrhythmics e.g. amiodarone, bepridil, disopyramide, flecainide…»FDA, section 7 · Open on DailyMed
«- Medicamentos cardiovasculares que prolongan el intervalo QT (ej. quinidina, disopiramida,»AEMPS, section 4.5 · Open on CIMA
«CYP2D6 Inhibitors: Drugs that are strong inhibitors of CYP2D6 such as quinidine, fluoxetine, paroxetine, and propafenone were shown to double metoprolol concentrations. While there is no information…»FDA, section 7 · Open on DailyMed
«Antiarrítmicos de clase I (quinidina, hidroquinidina, cibenzolina, flecainida, disopiramida, lidocaína, mexiletina, propafenona): puede potenciarse el efecto sobre el tiempo de conducción…»AEMPS, section 4.5 · Open on CIMA
«CYP2D6 and CYP3A4 Inhibitors: Small doses of quinidine completely inhibit the CYP2D6 hydroxylation metabolic pathway, making all patients, in effect, slow metabolizers [see Clinical Pharmacology (…»FDA, section 7 · Open on DailyMed
«Antiarrhythmics and Other QT Prolonging Drugs: Discontinue Class I or Class III antiarrhythmic agents for at least three half-lives prior to dosing with sotalol. Class Ia antiarrhythmic drugs, such…»FDA, section 7 · Open on DailyMed
«Inhibidores del CYP2D6: En publicaciones científicas se han descrito interacciones farmacocinéticas con inhibidores del CYP2D6, mostrando una reducción del 65-75% en los niveles plasmáticos de una de…»AEMPS, section 4.5 · Open on CIMA
«Ciclosporina (inhibidor de la P-gp y el CYP3A): No hay datos disponibles sobre el uso concomitante de ticagrelor con otros principios activos que también son inhibidores potentes de la P-gp e…»AEMPS, section 4.5 · Open on CIMA
«Efectos en el intervalo QTc: Se desconoce la relevancia clínica de este hallazgo y no puede generalizarse a todo tipo de pacientes en cualquier circunstancia, ya que dependerá de los factores de…»AEMPS, section 4.4 · Open on CIMA
«Uso con medicamentos que prolongan el intervalo QT: Debido a que el tratamiento de deprivación de andrógenos puede prolongar el intervalo QT, se recomienda precaución cuando se administre abiraterona…»AEMPS, section 4.5 · Open on CIMA
«Cuando se prescribe amisulprida con medicamentos que prolongan el intervalo QT por ejemplo antiarritmicos de la clase IA (por ejemplo, quinidina, disopiramida) y antiarritmicos de la clase III (por…»AEMPS, section 4.5 · Open on CIMA
«Medicamentos asociados con prolongación del intervalo QT: Azitromicina se debe usar con precaución en pacientes que reciben medicamentos que se sabe que prolongan el intervalo QT (ver sección 4.4)…»AEMPS, section 4.5 · Open on CIMA
«Sustancias que pueden desencadenar torsades de pointes: - antiarrítmicos de clase Ia (por ejemplo, quinidina, hidroquinidina, disopiramida)»AEMPS, section 4.5 · Open on CIMA
«Interacciones basadas en CYP3A: Se pueden considerar ajustes de dosis y cuando sea posible, las concentraciones séricas de los fármacos metabolizados principalmente por CYP3A se deben controlar de…»AEMPS, section 4.5 · Open on CIMA
«Potential for Other Drugs to Affect Clozapine: Concomitant treatment with clozapine and CYP2D6 or CYP3A4 inhibitors (e.g., cimetidine, escitalopram, erythromycin, paroxetine, bupropion, fluoxetine…»FDA, section 7 · Open on DailyMed
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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.
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.
Direct links to regulator labels. Open in a new tab.
Ranolazine, Amiodarone, Ubidecarenone (coenzyme Q10), Digoxin, Dofetilide, Isosorbide dinitrate, Lidocaine, Disopyramide