Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DISOPYRAMIDE PHOSPHATE vs CIN-QUIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Class Ia antiarrhythmic agent; inhibits cardiac sodium channels, prolongs action potential duration, increases effective refractory period, and reduces myocardial excitability and conduction velocity.
Cin-Quin (quinidine) is a class Ia antiarrhythmic agent that blocks sodium channels, prolonging the effective refractory period and slowing conduction velocity. It also has anticholinergic and alpha-adrenergic blocking properties.
Treatment of life-threatening ventricular arrhythmias (e.g., sustained ventricular tachycardia),Suppression of symptomatic atrial fibrillation/flutter
Treatment of atrial fibrillation and flutter,Paroxysmal supraventricular tachycardia,Ventricular arrhythmias,Maintenance of sinus rhythm after cardioversion
100-200 mg orally every 6 hours; immediate-release: 100-200 mg every 6 hours; extended-release: 200-300 mg every 12 hours.
Quinine sulfate 648 mg (two 324 mg capsules) orally every 8 hours for 7 days, in combination with doxycycline, tetracycline, or clindamycin.
Terminal elimination half-life: 6-8 hours (normal renal function); prolonged to 15-25 hours in renal impairment (creatinine clearance <40 m L/min), requiring dose adjustment.
Terminal elimination half-life is approximately 4-5 hours in healthy volunteers; prolonged to 8-12 hours in severe malaria or hepatic impairment.
Primarily hepatic metabolism via CYP3A4; approximately 40-60% excreted unchanged in urine.
Metabolized primarily by CYP3A4 to active metabolites (3-hydroxyquinidine and quinidine-N-oxide).
Renal excretion of unchanged drug accounts for 40-60% of elimination; hepatic metabolism (N-dealkylation) accounts for 20-30%; approximately 10-15% excreted in feces via biliary elimination.
Primarily hepatic metabolism; renal excretion of unchanged drug <20%. Biliary/fecal excretion accounts for ~30% of total clearance.
50-65% bound to plasma proteins (primarily to alpha-1-acid glycoprotein, with lower affinity to albumin).
Approximately 70-80% bound, primarily to alpha-1-acid glycoprotein and, to a lesser extent, albumin.
0.8-1.4 L/kg (extensive tissue distribution; higher in myocardial tissue than plasma).
Apparent volume of distribution (Vd) is 1.5-2.5 L/kg, indicating extensive tissue distribution.
Oral: 80-90% (immediate-release); 60-80% (sustained-release due to incomplete absorption).
Oral bioavailability is approximately 80% in healthy subjects; may be reduced in patients with malaria due to impaired absorption.
GFR 30-50 m L/min: 100 mg every 8-12 hours; GFR 15-29 m L/min: 100 mg every 12-24 hours; GFR <15 m L/min or dialysis: 100 mg every 24 hours or 50 mg every 12 hours.
No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (GFR <10 m L/min), reduce dose by one-third to one-half (e.g., 324 mg every 8 hours) and monitor for toxicity.
Child-Pugh class B: reduce dose by 50%; Child-Pugh class C: avoid use or reduce by 75%.
No specific guidelines for Child-Pugh classification; use with caution in severe hepatic impairment (Child-Pugh C) and consider dose reduction by 50% based on clinical response and monitoring of serum levels.
Children <1 year: 10-30 mg/kg/day divided every 6 hours; 1-4 years: 10-30 mg/kg/day divided every 6 hours; 4-12 years: 10-30 mg/kg/day divided every 6 hours; adolescents: same as adult dosing up to 400 mg/day.
For malaria: quinine sulfate 10 mg/kg (base) orally every 8 hours for 7 days (maximum 650 mg/dose) in combination with a second agent.
Start at low end of dosing range (100 mg every 6 hours) due to decreased renal function and increased sensitivity; monitor QTc interval and anticholinergic effects.
No specific dose adjustments recommended, but start at lower end of dosing range (e.g., 324 mg every 8 hours) due to age-related renal function decline and increased risk of QT prolongation.
Disopyramide has negative inotropic effects and may precipitate or exacerbate heart failure. Use with caution in patients with pre-existing heart failure or significant left ventricular dysfunction.
Quinidine has been associated with thrombocytopenic purpura and may exacerbate arrhythmias (proarrhythmia). It should be used with caution in patients with severe heart disease or preexisting arrhythmias.
May worsen or precipitate heart failure due to negative inotropy,Risk of proarrhythmia (e.g., torsades de pointes) especially with hypokalemia or bradycardia,Anticholinergic effects: urinary retention, dry mouth, blurred vision, constipation,May cause hypoglycemia in rare cases,Dose adjustment required in renal or hepatic impairment
May cause QT prolongation and torsades de pointes, especially in patients with hypokalemia, hypomagnesemia, or bradycardia,Cinchonism (tinnitus, hearing loss, blurred vision, nausea) may occur at high doses,Hepatic toxicity and hypersensitivity reactions (including thrombocytopenia),Monitor serum potassium and magnesium levels,Avoid use with other drugs that prolong QT interval
Cardiogenic shock,Pre-existing second- or third-degree AV block (without pacemaker),Known hypersensitivity to disopyramide,Severe heart failure or left ventricular dysfunction
Hypersensitivity to quinidine or cinchona alkaloids,Complete AV block without pacemaker,Myasthenia gravis,Digitalis toxicity,History of drug-induced torsades de pointes or QT prolongation
Avoid grapefruit juice as it may increase disopyramide concentrations. Limit caffeine intake as it may worsen arrhythmias. Avoid high-fat meals as they may reduce absorption.
Avoid grapefruit and grapefruit juice (increases quinidine exposure). Limit caffeine intake as quinidine may enhance its effects. Maintain adequate potassium and magnesium intake; hypokalemia and hypomagnesemia increase arrhythmia risk.
Disopyramide crosses the placenta. First trimester: No well-controlled studies; potential for adverse effects based on animal data. Second and third trimesters: May stimulate uterine contractions, potentially causing preterm labor; reports of neonatal hypoglycemia and respiratory depression. Not recommended during pregnancy unless benefit outweighs risk.
CIN-QUIN (quinine) is contraindicated in pregnancy due to teratogenicity. First trimester: risk of congenital malformations (e.g., auditory nerve hypoplasia, limb defects). Second and third trimesters: may cause fetal hypoxia and hypoglycemia; avoid use for malaria prophylaxis. Only in severe falciparum malaria when no alternative exists.
Disopyramide is excreted into breast milk with milk-to-plasma ratio of approximately 0.9. Infant exposure estimated at 2–6% of maternal weight-adjusted dose. Monitor infant for bradycardia, hypoglycemia, and apnea. Weigh benefits against potential risks.
Quinine is excreted into breast milk in small amounts. M/P ratio approximately 0.2-0.5. Limited data suggest low risk to infant; however, monitor for signs of cinchonism (e.g., fever, rash, restlessness).
Dose may require adjustment due to pregnancy-induced pharmacokinetic changes (increased volume of distribution, enhanced renal clearance, altered protein binding). Monitor serum disopyramide levels and therapeutic response; consider lower starting doses and titrate to effect.
Pregnancy increases clearance and volume of distribution of quinine; dose adjustments are not well-defined. For severe malaria, standard dosing (600 mg oral quinine sulfate every 8 hours for 7 days) is used, but therapeutic drug monitoring is recommended.
Disopyramide is a class IA antiarrhythmic with significant negative inotropic and anticholinergic effects. Avoid in patients with heart failure, cardiogenic shock, or glaucoma. Dose adjustment required in renal impairment. Monitor QRS and QT intervals; proarrhythmia risk. May cause hypoglycemia in elderly or diabetic patients. Therapeutic drug monitoring recommended (target 2-5 mcg/m L).
Cin-Quin is a brand of quinidine, a class Ia antiarrhythmic. Monitor QTc interval; risk of torsades de pointes. Avoid in patients with myasthenia gravis due to neuromuscular blocking effects. Use with caution in hepatic impairment. Can cause cinchonism (tinnitus, headache, nausea).
Take exactly as prescribed; do not skip doses or double up.,Do not take with grapefruit juice.,Avoid alcohol and other CNS depressants.,Report symptoms of heart failure (shortness of breath, swelling) or arrhythmia (palpitations, syncope).,May cause dry mouth, blurred vision, urinary retention; use caution driving.,Monitor blood sugar if diabetic.,Do not stop abruptly without consulting your doctor.
Take exactly as prescribed; do not skip doses or double up.,Report any rapid or irregular heartbeat, fainting, or severe dizziness.,Avoid grapefruit juice as it can increase quinidine levels.,Do not use with over-the-counter products containing quinine or quinidine.,Tell your doctor if you have liver disease, myasthenia gravis, or low potassium/magnesium.,Quinidine can cause diarrhea; contact your doctor if persistent.,You may experience ringing in the ears or blurred vision; notify your prescriber.
"Disopyramide, a class Ia antiarrhythmic agent, prolongs the QT interval by inhibiting cardiac potassium channels, thereby increasing the risk of torsades de pointes. Paroxetine, a selective serotonin reuptake inhibitor (SSRI), also has dose-dependent QT-prolonging effects, primarily through hERG channel blockade. Concomitant use synergistically lengthens the QT interval, predisposing patients to potentially fatal ventricular arrhythmias, especially in those with pre-existing risk factors such as hypokalemia, bradycardia, or genetic long QT syndrome."
"Disopyramide, a class Ia antiarrhythmic agent, prolongs ventricular repolarization by blocking cardiac sodium and potassium channels. Ezogabine, a potassium channel opener, also has dose-dependent effects on cardiac repolarization. Coadministration may result in additive QT interval prolongation, increasing the risk of torsade de pointes and other ventricular arrhythmias."
"Disopyramide, a class Ia antiarrhythmic agent, may potentiate the hypoglycemic effects of cinoxacin, a quinolone antibiotic, by enhancing insulin secretion and increasing peripheral glucose uptake. This interaction can lead to clinically significant hypoglycemia, particularly in patients with diabetes mellitus or those concurrently using other hypoglycemic agents. Patients may experience symptoms such as diaphoresis, palpitations, confusion, or loss of consciousness if blood glucose levels drop precipitously."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about DISOPYRAMIDE PHOSPHATE vs CIN-QUIN, answered by our medical review team.
DISOPYRAMIDE PHOSPHATE is a Antiarrhythmic (Class Ia) that works by Class Ia antiarrhythmic agent; inhibits cardiac sodium channels, prolongs action potential duration, increases effective refractory period, and reduces myocardial excitability and conduction velocity.. CIN-QUIN is a Antiarrhythmic (Class Ia) that works by Cin-Quin (quinidine) is a class Ia antiarrhythmic agent that blocks sodium channels, prolonging the effective refractory period and slowing conduction velocity. It also has anticholinergic and alpha-adrenergic blocking properties.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between DISOPYRAMIDE PHOSPHATE and CIN-QUIN depend on the specific clinical indication. These are both Antiarrhythmic (Class Ia) agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of DISOPYRAMIDE PHOSPHATE is: 100-200 mg orally every 6 hours; immediate-release: 100-200 mg every 6 hours; extended-release: 200-300 mg every 12 hours.. The standard adult dose of CIN-QUIN is: Quinine sulfate 648 mg (two 324 mg capsules) orally every 8 hours for 7 days, in combination with doxycycline, tetracycline, or clindamycin.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between DISOPYRAMIDE PHOSPHATE and CIN-QUIN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. DISOPYRAMIDE PHOSPHATE is classified as Category D/X. Disopyramide crosses the placenta. First trimester: No well-controlled studies; potential for adverse effects based on animal data. Second and third trimesters: May stimulate uteri. CIN-QUIN is classified as Category C. CIN-QUIN (quinine) is contraindicated in pregnancy due to teratogenicity. First trimester: risk of congenital malformations (e.g., auditory nerve hypoplasia, limb defects). Second . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.