CARDIOQUIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).

How it works

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.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).

Breastfeeding	Quinidine is excreted into breast milk with a milk-to-plasma ratio of approximately 0.7-0.9. Limited data suggest low risk to nursing infant, but monitor for arrhythmias, cinchonism, and thrombocytopenia. Use with caution.
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.

Warnings & precautions

■ 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.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Complete AV block without pacemaker","Long QT syndrome","Myasthenia gravis","Hypersensitivity to quinine/quinidine","Cardiogenic shock","Digitalis toxicity"]

Clinical Precautions

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 Tips & Counseling

Drug interactions

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CARDIOQUIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).

How it works

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for CARDIOQUIN (CARDIOQUIN).

Breastfeeding	Quinidine is excreted into breast milk with a milk-to-plasma ratio of approximately 0.7-0.9. Limited data suggest low risk to nursing infant, but monitor for arrhythmias, cinchonism, and thrombocytopenia. Use with caution.
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.

Warnings & precautions

■ 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.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Complete AV block without pacemaker","Long QT syndrome","Myasthenia gravis","Hypersensitivity to quinine/quinidine","Cardiogenic shock","Digitalis toxicity"]

Clinical Precautions

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 Tips & Counseling

Drug interactions

Loading safety data…

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.