Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
TIKOSYN vs QUINIDEX
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 (fast inward sodium current) and prolongs action potential duration; also has 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,Maintenance of sinus rhythm after cardioversion,Treatment of ventricular arrhythmias (off-label)
500 mcg orally twice daily for atrial fibrillation/flutter conversion and maintenance of sinus rhythm.
Quinidine sulfate (QUINIDEX): 200-400 mg orally every 6 hours as arrhythmia suppression; maximum 4 g/day. Route: oral, frequency: every 6 hours.
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 is 6-8 hours in adults with normal renal and hepatic function; may be prolonged to 10-12 hours in congestive heart failure or hepatic impairment.
Primarily metabolized by CYP3A4; also undergoes N-dealkylation and glucuronidation; renal excretion of unchanged drug (20-30%) and metabolites.
Primarily hepatic via CYP3A4 (major) and CYP2C9 (minor) to active metabolites (3-hydroxyquinidine, quinidine-N-oxide); also renal excretion of unchanged drug (20%).
Renal: 80% as unchanged drug; biliary/fecal: 20% (metabolites and minor parent drug).
Renal excretion accounts for approximately 20% unchanged drug; hepatic metabolism (primarily CYP3A4) accounts for 80% with metabolites excreted renally and biliarily; about 5% excreted in feces.
96% bound to plasma proteins (primarily albumin).
80-90% bound to plasma proteins: primarily albumin and alpha-1-acid glycoprotein.
3 L/kg (range 2-4 L/kg), indicating extensive tissue distribution, particularly to cardiac tissue.
2-4 L/kg; extensive tissue distribution with high affinity for myocardium (tissue-to-plasma ratio >10).
>90% after oral administration (approximately 93% with low first-pass metabolism).
70-80% for immediate-release oral; 50-70% for sustained-release formulations due to first-pass metabolism; absorption reduced by food.
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 6 hours. Cr Cl 10-29 m L/min: administer 50% of normal dose every 8 hours. Cr Cl <10 m L/min: administer 50% of normal dose every 12 hours.
No formal Child-Pugh based adjustment; use caution in severe hepatic impairment due to limited data.
Child-Pugh class A: no adjustment. Child-Pugh class B: reduce dose by 50%; monitor levels. Child-Pugh class C: contraindicated or use with extreme caution; reduce dose by 75% with therapeutic drug monitoring.
Safety and efficacy not established in pediatric patients.
Oral: 15-60 mg/kg/day in 4-5 divided doses; maximum single dose 600 mg. For chronic suppression: start 30 mg/kg/day in 4-5 divided doses.
Adjust based on renal function per Cr Cl; monitor QTc interval closely due to increased risk of toxicity.
Start at lower end of dosing range (200 mg every 8 hours) due to decreased hepatic and renal function; adjust based on plasma levels and QT interval monitoring.
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.
Increased mortality in treatment of non-life-threatening ventricular arrhythmias; proarrhythmic effects (torsades de pointes).
QTc prolongation; hypokalemia; hypomagnesemia; renal impairment; bradycardia; concurrent use of other QT-prolonging drugs; drug interactions with CYP3A4 inhibitors.
Proarrhythmia (torsades de pointes), hepatotoxicity, cinchonism, hypersensitivity reactions, worsening of heart failure, digitalis toxicity, incomplete AV block, electrolyte disturbances.
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.
Hypersensitivity to quinidine or cinchona alkaloids, complete AV block or severe intraventricular conduction defects, myasthenia gravis, history of thrombocytopenia with quinidine, concurrent use with drugs that prolong QT interval (unless absolutely necessary).
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.
Grapefruit juice increases quinidine bioavailability and serum levels, raising toxicity risk. Avoid grapefruit and grapefruit juice. Alkaline foods (e.g., antacids, milk) may increase quinidine absorption. High-sodium diet may enhance potassium loss and worsen arrhythmias. Avoid excessive caffeine or stimulants.
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.
First trimester: Limited data, but quinidine crosses placenta. No clear increase in major malformations after first trimester exposure. Second and third trimesters: Risk of fetal QT prolongation, neonatal thrombocytopenia, and tachycardia. Fetal distress may occur. Avoid if alternative exists, but if needed, monitor fetal ECG and heart rate.
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. M/P ratio reported as 0.57–0.78. Amount is low, but monitor infant for arrhythmias, bruising, and bleeding. Generally considered compatible with breastfeeding if maternal monitoring is done.
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 may require dose increases. Protein binding decreases, potentially lowering total drug concentrations. Monitor free drug levels if possible. adjust dose based on therapeutic drug monitoring and clinical response. Close monitoring recommended.
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.
Quinidine (as Quinidex) is a class Ia antiarrhythmic; monitor QRS and QT intervals due to risk of torsades de pointes. It also has anticholinergic properties, causing diarrhea in up to 50% of patients, which can be dose-limiting. Drug interactions are critical: quinidine inhibits CYP2D6, increasing levels of digoxin, warfarin, and many beta-blockers. Consider checking serum quinidine levels (therapeutic: 2-6 mcg/m L) and ECG if initiating or adjusting dose.
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 double dose if missed.,Avoid grapefruit juice as it can increase quinidine levels and toxicity.,Report new or worsening palpitations, dizziness, syncope, or irregular heartbeat immediately.,May cause diarrhea; contact your prescriber if diarrhea becomes severe or persistent.,Quinidine can cause blurred vision, tinnitus, or headache; report these to your doctor.,Avoid over-the-counter medications without consulting your doctor (especially antacids, antihistamines, and cold remedies).
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 QUINIDEX, 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.. QUINIDEX is a Antiarrhythmic Agent that works by Class Ia antiarrhythmic agent; blocks sodium channels (fast inward sodium current) and prolongs action potential duration; also has anticholinergic and negative inotropic effects.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between TIKOSYN and QUINIDEX 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 QUINIDEX is: Quinidine sulfate (QUINIDEX): 200-400 mg orally every 6 hours as arrhythmia suppression; maximum 4 g/day. Route: oral, frequency: every 6 hours.. 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 QUINIDEX 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. QUINIDEX is classified as Category C. First trimester: Limited data, but quinidine crosses placenta. No clear increase in major malformations after first trimester exposure. Second and third trimesters: Risk of fetal Q. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.