CARDIOQUIN
Clinical safety rating
cautionComprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).
Class IA antiarrhythmic agent; blocks sodium channels, slows phase 0 depolarization, prolongs action potential duration, and increases effective refractory period. Also exhibits anticholinergic and negative inotropic effects.
| Metabolism | Primarily hepatic via CYP3A4; also metabolized by CYP2D6 to active metabolite (3-hydroxyquinidine). |
| Excretion | Renal: 60-80% as unchanged drug and metabolites (primarily hydroxylated metabolites). Biliary/fecal: 20-40%. |
| Half-life | Terminal elimination half-life: 6-8 hours in patients with normal renal function. Prolonged in renal impairment (up to 16-40 hours) and heart failure, requiring dose adjustment. |
| Protein binding | 80-90% bound, primarily to alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | Vd: 2-3 L/kg. Large Vd indicates extensive tissue distribution, with high affinity for myocardial tissue. |
| Bioavailability | Oral: 70-85% (may be reduced in heart failure). Intravenous: 100%. |
| Onset of Action | Oral: 1-3 hours for peak plasma concentration; therapeutic effect on atrial fibrillation typically within 2-4 hours. Intravenous: 10-12 minutes for arrhythmia suppression. |
| Duration of Action | Oral: 6-8 hours (sustained-release: 8-12 hours). Duration is dose-dependent and influenced by cardiac output and renal function. |
| Molecular Weight | 324.42 |
Quinidine gluconate extended-release: 324-648 mg orally every 8-12 hours. Quinidine sulfate immediate-release: 200-400 mg orally every 6 hours. Quinidine sulfate extended-release: 300-600 mg orally every 8-12 hours. Maximum dose: 3-4 g/day.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-50 mL/min: administer 75% of normal dose every 8-12 hours. CrCl 10-29 mL/min: administer 50% of normal dose every 8-12 hours. CrCl <10 mL/min: administer 30% of normal dose every 8-12 hours. Hemodialysis: administer after dialysis on dialysis days. |
| Liver impairment | Child-Pugh Class A: no adjustment necessary. Child-Pugh Class B: reduce dose by 25% and monitor QT interval. Child-Pugh Class C: reduce dose by 50% and monitor QT interval closely. |
| Pediatric use | For supraventricular tachyarrhythmias: Quinidine sulfate 15-60 mg/kg/day orally divided every 6 hours; Quinidine gluconate 15-60 mg/kg/day orally divided every 8-12 hours. Maximum single dose: 400 mg. Maximum daily dose: 3 g. |
| Geriatric use | Initiate at lower doses (e.g., quinidine sulfate 200 mg orally every 8-12 hours) and titrate slowly due to decreased renal function and increased risk of QT prolongation and cinchonism. Monitor serum creatinine, QT interval, and quinidine levels. Adjust dose based on renal function. |
| 1st trimester | Cardioquin (quinidine) crosses the placenta. Limited human data; animal studies show no consistent teratogenicity. Use only if clearly needed and benefit outweighs risk. |
| 2nd trimester | Consider fetal risks; monitor maternal QT interval. Avoid near term due to potential for neonatal arrhythmias. |
| 3rd trimester | May cause neonatal toxicity (arrhythmias, hypoglycemia). Avoid use during labor and delivery. |
Clinical note
Comprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).
| Placental transfer | Crosses placenta; fetal concentrations similar to maternal. |
| Breastfeeding | Quinidine is excreted into breast milk in small amounts (milk:plasma ratio ~0.7). Monitor infant for arrhythmias, cinchonism, and hemolytic anemia. Use with caution; alternative agents preferred. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Quinidine, the active ingredient in CARDIOQUIN, is classified as FDA Pregnancy Category C. First trimester: Limited data, but animal studies have shown teratogenic effects at high doses. Second and third trimesters: No adequate well-controlled studies; potential risk of fetal tachycardia, thrombocytopenia, and neonatal coagulopathy. Use only if potential benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal ECG, serum quinidine levels (therapeutic range 2-6 mcg/mL), electrolytes, and renal function. Assess fetal heart rate and growth with ultrasound; consider fetal ECG if arrhythmias suspected. |
| Fertility Effects | No specific data on human fertility. Animal studies have shown decreased spermatogenesis at high doses. Impact on female fertility not established. |
■ FDA Black Box Warning
May cause fatal arrhythmias (e.g., torsade de pointes, ventricular fibrillation) especially in patients with structural heart disease, hypokalemia, or bradycardia.
| Serious Effects |
Hypersensitivity to quinidine or cinchona alkaloidsThrombocytopenic purpura related to quinidineMyasthenia gravisUncompensated heart failureComplete AV block without a pacemakerDigitalis toxicityProlonged QT interval
| Precautions | Risk of proarrhythmia; monitor ECG, electrolytes, hepatic/renal function; avoid in QT prolongation; may cause cinchonism (tinnitus, hearing loss, visual disturbances); caution in myasthenia gravis, heart failure, and hepatic impairment. |
| Food/Dietary | Avoid grapefruit and grapefruit juice; they inhibit CYP3A4 metabolism, increasing quinidine levels. Take with food to reduce gastrointestinal upset, but avoid high-potassium foods (e.g., bananas, oranges, spinach) if potassium levels are low. |
| Clinical Pearls | Cardioquin (quinidine) is a class Ia antiarrhythmic. Monitor QRS and QT intervals; risk of torsades de pointes, especially with hypokalemia or hypomagnesemia. Coadministration with digoxin requires digoxin dose reduction due to decreased clearance. Avoid in patients with myasthenia gravis, as it can exacerbate weakness. Use with caution in hepatic impairment. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop without consulting your doctor. · Report any fainting, rapid heartbeat, or chest pain immediately. · Avoid grapefruit and grapefruit juice; they increase quinidine levels and risk of side effects. · Limit alcohol intake; it may increase side effects like dizziness and drowsiness. · Notify all healthcare providers you are taking quinidine. |
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