Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
TIKOSYN vs CARDIOQUIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Selective class III antiarrhythmic agent; blocks cardiac potassium channels (IKr), prolonging action potential duration and effective refractory period.
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.
Conversion of atrial fibrillation/atrial flutter to normal sinus rhythm,Maintenance of normal sinus rhythm in patients with symptomatic atrial fibrillation/atrial flutter
Conversion and prevention of atrial fibrillation/flutter,Suppression of ventricular arrhythmias,Maintenance of sinus rhythm after cardioversion
500 mcg orally twice daily for atrial fibrillation/flutter conversion and maintenance of sinus rhythm.
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.
10 hours (terminal) in patients with normal renal function; prolonged to up to 42 hours in severe renal impairment; clinically relevant for dosing interval adjustment.
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.
Primarily metabolized by CYP3A4; also undergoes N-dealkylation and glucuronidation; renal excretion of unchanged drug (20-30%) and metabolites.
Primarily hepatic via CYP3A4; also metabolized by CYP2D6 to active metabolite (3-hydroxyquinidine).
Renal: 80% as unchanged drug; biliary/fecal: 20% (metabolites and minor parent drug).
Renal: 60-80% as unchanged drug and metabolites (primarily hydroxylated metabolites). Biliary/fecal: 20-40%.
96% bound to plasma proteins (primarily albumin).
80-90% bound, primarily to alpha-1-acid glycoprotein (AAG) and albumin.
3 L/kg (range 2-4 L/kg), indicating extensive tissue distribution, particularly to cardiac tissue.
Vd: 2-3 L/kg. Large Vd indicates extensive tissue distribution, with high affinity for myocardial tissue.
>90% after oral administration (approximately 93% with low first-pass metabolism).
Oral: 70-85% (may be reduced in heart failure). Intravenous: 100%.
Cr Cl > 60 m L/min: 500 mcg BID. Cr Cl 40-60 m L/min: 250 mcg BID. Cr Cl < 40 m L/min: contraindicated.
Cr Cl 30-50 m L/min: administer 75% of normal dose every 8-12 hours. Cr Cl 10-29 m L/min: administer 50% of normal dose every 8-12 hours. Cr Cl <10 m L/min: administer 30% of normal dose every 8-12 hours. Hemodialysis: administer after dialysis on dialysis days.
No formal Child-Pugh based adjustment; use caution in severe hepatic impairment due to limited data.
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.
Safety and efficacy not established in pediatric patients.
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.
Adjust based on renal function per Cr Cl; monitor QTc interval closely due to increased risk of toxicity.
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.
Tikosyn can cause life-threatening ventricular arrhythmias (e.g., torsade de pointes) and must be initiated in a hospital setting with continuous ECG monitoring and dose adjustment based on creatinine clearance and QTc interval.
May cause fatal arrhythmias (e.g., torsade de pointes, ventricular fibrillation) especially in patients with structural heart disease, hypokalemia, or bradycardia.
QTc prolongation; hypokalemia; hypomagnesemia; renal impairment; bradycardia; concurrent use of other QT-prolonging drugs; drug interactions with CYP3A4 inhibitors.
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.
Baseline QTc > 440 msec (500 msec in ventricular conduction abnormalities); severe renal impairment (Cr Cl < 20 m L/min); concurrent use of verapamil, cimetidine, ketoconazole, trimethoprim, or other drugs that prolong QT; congenital long QT syndrome; history of torsade de pointes; hypersensitivity to dofetilide.
Complete AV block without pacemaker,Long QT syndrome,Myasthenia gravis,Hypersensitivity to quinine/quinidine,Cardiogenic shock,Digitalis toxicity
Grapefruit juice inhibits CYP3A4, increasing dofetilide levels and risk of arrhythmia; avoid grapefruit and grapefruit juice. High-potassium foods (e.g., bananas, oranges, spinach) are generally safe but must be consumed consistently to avoid electrolyte fluctuations. Avoid excessive licorice intake which can cause hypokalemia.
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.
Pregnancy Category C. Animal studies have shown fetal toxicity (increased fetal loss, reduced fetal weight) at maternally toxic doses. No adequate and well-controlled studies in pregnant women. Potential fetal risks in all trimesters; use only if benefit justifies 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.
Not recommended. It is unknown if TIKOSYN is excreted in human milk. M/P ratio not available. Potential for serious adverse reactions in nursing infants; discontinue nursing or drug.
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.
Dosing adjustments not specifically defined for pregnancy. Use standard dosing based on renal function and QTc interval. However, due to potential pharmacokinetic changes in pregnancy (increased volume of distribution, altered clearance), monitor drug levels (if available) and adjust dose cautiously, targeting therapeutic QTc effect.
Increased volume of distribution and renal clearance in pregnancy may require dose adjustments. Monitor serum quinidine levels and titrate to therapeutic effect. Lower starting doses may be needed due to altered protein binding.
TIKOSYN (dofetilide) is a class III antiarrhythmic indicated for maintenance of sinus rhythm in patients with atrial fibrillation/flutter. Requires inpatient initiation with continuous ECG monitoring due to risk of torsade de pointes. Dosing is based on creatinine clearance and QTc interval; must not exceed 500 mcg twice daily. Drug interactions via CYP3A4 and renal clearance are critical; avoid verapamil, cimetidine, ketoconazole, and trimethoprim. Hypokalemia and hypomagnesemia must be corrected before use.
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.
You must be hospitalized for the first 3 days of treatment to monitor your heart rhythm.,Do not take any new medications, including over-the-counter drugs or herbal supplements, without consulting your doctor.,Report any fainting, lightheadedness, or palpitations immediately.,Take your dose exactly as prescribed, usually twice daily with or without food.,Do not skip doses or double up if you miss a dose; call your doctor if you miss more than one dose.,Avoid grapefruit juice and grapefruit products while on this medication.,Your kidney function will be checked regularly; keep all lab appointments.,Inform all healthcare providers that you are taking TIKOSYN.
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.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about TIKOSYN vs CARDIOQUIN, answered by our medical review team.
TIKOSYN is a Antiarrhythmic Agent that works by Selective class III antiarrhythmic agent; blocks cardiac potassium channels (IKr), prolonging action potential duration and effective refractory period.. CARDIOQUIN is a Antiarrhythmic Agent that works by 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between TIKOSYN and CARDIOQUIN depend on the specific clinical indication. These are both Antiarrhythmic Agent agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of TIKOSYN is: 500 mcg orally twice daily for atrial fibrillation/flutter conversion and maintenance of sinus rhythm.. The standard adult dose of CARDIOQUIN is: 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.. 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 TIKOSYN and CARDIOQUIN 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. TIKOSYN is classified as Category C. Pregnancy Category C. Animal studies have shown fetal toxicity (increased fetal loss, reduced fetal weight) at maternally toxic doses. No adequate and well-controlled studies in pr. CARDIOQUIN is classified as Category C. 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 . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.