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Quick facts
- Drug class
- Antiarrhythmic [EPC]
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 310003
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
INDICATIONS AND USAGE Maintenance of Normal Sinus Rhythm (Delay in AF/AFl Recurrence) Dofetilide capsules are indicated for the maintenance of normal sinus rhythm (delay in time to recurrence of atrial fibrillation/atrial flutter [AF/AFl]) in patients with atrial fibrillation/atrial flutter of greater than one week duration who have been converted to normal sinus rhythm. Because dofetilide capsules can cause life threatening ventricular arrhythmias, it should be reserved for patients in whom atrial fibrillation/atrial flutter is highly symptomatic. In general, antiarrhythmic therapy for atrial fibrillation/atrial flutter aims to prolong the time in normal sinus rhythm. Recurrence is expected in some patients (see CLINICAL STUDIES ). Conversion of Atrial Fibrillation/Flutter Dofetilide capsules are indicated for the conversion of atrial fibrillation and atrial flutter to normal sinus rhythm. Dofetilide capsules have not been shown to be effective in patients with paroxysmal atrial fibrillation.
About this medicine
DESCRIPTION Dofetilide capsules are an antiarrhythmic drug with Class III (cardiac action potential duration prolonging) properties. Its empirical formula is C 19 H 27 N 3 O 5 S 2 and it has a molecular weight of 441.6. The structural formula is The chemical name for dofetilide is: N -[4-[2-[methyl[2-[4-[(methylsulfonyl)amino]phenoxy]ethyl]amino]ethyl]phenyl]methanesulfonamide. Dofetilide is a white to off-white powder. It is very slightly soluble in water and propan-2-ol and is soluble in 0.1M aqueous sodium hydroxide, acetone, and aqueous 0.1M hydrochloric acid. Dofetilide capsules contain the following inactive ingredients: microcrystalline cellulose, corn starch, colloidal silicon dioxide and magnesium stearate. The capsule shells contain gelatin, titanium dioxide, red iron oxide, yellow iron oxide, and black ink. The imprint ink contains iron oxide black, shellac, ethanol, n-butyl alcohol, isopropyl alcohol, propylene glycol, and ammonium hydroxide. Dofetilide capsules are supplied for oral administration in three dosage strengths: 125 mcg (0.125 mg) dark caramel and white capsules, 250 mcg (0.25 mg) light orange capsules, and 500 mcg (0.5 mg) light orange and white capsules. Chemical Structure
How it works
Mechanism of Action Dofetilide shows Vaughan Williams Class III antiarrhythmic activity. The mechanism of action is blockade of the cardiac ion channel carrying the rapid component of the delayed rectifier potassium current, I Kr . At concentrations covering several orders of magnitude, dofetilide blocks only I Kr with no relevant block of the other repolarizing potassium currents (e.g., I Ks , I K1 ). At clinically relevant concentrations, dofetilide has no effect on sodium channels (associated with Class I effect), adrenergic alpha-receptors, or adrenergic beta-receptors.
Who should not take it
CONTRAINDICATIONS Dofetilide capsules are contraindicated in patients with congenital or acquired long QT syndromes. Dofetilide capsules should not be used in patients with a baseline QT interval or QTc >440 msec (500 msec in patients with ventricular conduction abnormalities). Dofetilide capsules are also contraindicated in patients with severe renal impairment (calculated creatinine clearance <20 mL/min). The concomitant use of verapamil or the cation transport system inhibitors cimetidine, trimethoprim (alone or in combination with sulfamethoxazole), or ketoconazole with dofetilide capsules is contraindicated (see WARNINGS and PRECAUTIONS, Drug-Drug Interactions ), as each of these drugs cause a substantial increase in dofetilide plasma concentrations. In addition, other known inhibitors of the renal cation transport system such as prochlorperazine, dolutegravir and megestrol should not be used in patients on dofetilide capsules. The concomitant use of hydrochlorothiazide (alone or in combinations such as with triamterene) with dofetilide capsules is contraindicated (see PRECAUTIONS, Drug-Drug Interactions ) because this has been shown to significantly increase dofetilide plasma concentrations and QT interval prolongation. Dofetilide capsules are also contraindicated in patients with a known hypersensitivity to the drug.
Warnings
WARNINGS Ventricular Arrhythmia Dofetilide capsules can cause serious ventricular arrhythmias, primarily Torsade de Pointes (TdP) type ventricular tachycardia, a polymorphic ventricular tachycardia associated with QT interval prolongation. QT interval prolongation is directly related to dofetilide plasma concentration. Factors such as reduced creatinine clearance or certain dofetilide drug interactions will increase dofetilide plasma concentration. The risk of TdP can be reduced by controlling the plasma concentration through adjustment of the initial dofetilide dose according to creatinine clearance and by monitoring the ECG for excessive increases in the QT interval. Treatment with dofetilide must therefore be started only in patients placed for a minimum of three days in a facility that can provide electrocardiographic monitoring and in the presence of personnel trained in the management of serious ventricular arrhythmias. Calculation of the creatinine clearance for all patients must precede administration of the first dose of dofetilide. For detailed instructions regarding dose selection, see DOSAGE AND ADMINISTRATION . The risk of dofetilide induced ventricular arrhythmia was assessed in three ways in clinical studies: 1) by description of the QT interval and its relation to the dose and plasma concentration of dofetilide; 2) by observing the frequency of TdP in dofetilide capsules-treated patients according to dose; 3) by observing the overall mortality rate in patients with atrial fibrillation and in patients with structural heart disease. Relation of QT Interval to Dose The QT interval increases linearly with increasing dofetilide capsules dose (see Figures 1 and 2 in CLINICAL PHARMACOLOGY and Dose-Response and Concentration Response for Increase in QT Interval ). Frequency of Torsade de Pointes In the supraventricular arrhythmia population (patients with AF and other supraventricular arrhythmias), the overall incidence of Torsade de Pointes was 0.8%. The frequency of TdP by dose is shown in Table 4. There were no cases of TdP on placebo. […]
Reported side effects
ADVERSE REACTIONS The dofetilide capsules clinical program involved approximately 8,600 patients in 130 clinical studies of normal volunteers and patients with supraventricular and ventricular arrhythmias. Dofetilide capsules were administered to 5,194 patients, including two large, placebo-controlled mortality trials (DIAMOND CHF and DIAMOND MI) in which 1,511 patients received dofetilide capsules for up to three years. In the following section, adverse reaction data for cardiac arrhythmias and non-cardiac adverse reactions are presented separately for patients included in the supraventricular arrhythmia development program and for patients included in the DIAMOND CHF and MI mortality trials (see CLINICAL STUDIES, Safety in Patients with Structural Heart Disease, DIAMOND Studies , for a description of these trials). In studies of patients with supraventricular arrhythmias, a total of 1,346 and 677 patients were exposed to dofetilide capsules and placebo for 551 and 207 patient years, respectively. A total of 8.7% of patients in the dofetilide groups were discontinued from clinical trials due to adverse events compared to 8.0% in the placebo groups. The most frequent reason for discontinuation (>1%) was ventricular tachycardia (2.0% on dofetilide vs. 1.3% on placebo). The most frequent adverse events were headache, chest pain, and dizziness. Serious Arrhythmias and Conduction Disturbances Torsade de Pointes is the only arrhythmia that showed a dose-response relationship to dofetilide capsules treatment. It did not occur in placebo treated patients. The incidence of Torsade de Pointes in patients with supraventricular arrhythmias was 0.8% (11/1346) (see WARNINGS ). The incidence of Torsade de Pointes in patients who were dosed according to the recommended dosing regimen (see DOSAGE AND ADMINISTRATION ) was 0.8% (4/525). Table 6 shows the frequency by randomized dose of serious arrhythmias and conduction disturbances reported as adverse events in patients with supraventricular arrhythmias. […]
Interactions with other medicines
Drug-Drug Interactions (see PRECAUTIONS ) Drug-Drug Interactions Cimetidine (see WARNINGS , CONTRAINDICATIONS ) Concomitant use of cimetidine is contraindicated. Cimetidine at 400 mg BID (the usual prescription dose) co-administered with dofetilide capsules (500 mcg BID) for 7 days has been shown to increase dofetilide plasma levels by 58%. Cimetidine at doses of 100 mg BID (OTC dose) resulted in a 13% increase in dofetilide plasma levels (500 mcg single dose). No studies have been conducted at intermediate doses of cimetidine. If a patient requires dofetilide capsules and anti-ulcer therapy, it is suggested that omeprazole, ranitidine, or antacids (aluminum and magnesium hydroxides) be used as alternatives to cimetidine, as these agents have no effect on the pharmacokinetic profile of dofetilide capsules. Verapamil (see CONTRAINDICATIONS ) Concomitant use of verapamil is contraindicated. Co-administration of dofetilide capsules with verapamil resulted in increases in dofetilide peak plasma levels of 42%, although overall exposure to dofetilide was not significantly increased. In an analysis of the supraventricular arrhythmia and DIAMOND patient populations, the concomitant administration of verapamil with dofetilide was associated with a higher occurrence of Torsade de Pointes. Ketoconazole (see WARNINGS , CONTRAINDICATIONS ) Concomitant use of ketoconazole is contraindicated. Ketoconazole at 400 mg daily (the maximum approved prescription dose) co-administered with dofetilide capsules (500 mcg BID) for 7 days has been shown to increase dofetilide C max by 53% in males and 97% in females, and AUC by 41% in males and 69% in females. Trimethoprim Alone or in Combination with Sulfamethoxazole (see WARNINGS , CONTRAINDICATIONS ) Concomitant use of trimethoprim alone or in combination with sulfamethoxazole is contraindicated. Trimethoprim 160 mg in combination with 800 mg sulfamethoxazole co-administered BID with dofetilide capsules (500 mcg BID) for 4 days has been shown to increase dofetilide AUC by 103% and C max by 93%. […]
If too much is taken
OVERDOSAGE There is no known antidote to dofetilide capsules; treatment of overdose should therefore be symptomatic and supportive. The most prominent manifestation of overdosage is likely to be excessive prolongation of the QT interval. In cases of overdose, cardiac monitoring should be initiated. Charcoal slurry may be given soon after overdosing but has been useful only when given within 15 minutes of dofetilide capsules administration. Treatment of Torsade de Pointes or overdose may include administration of isoproterenol infusion, with or without cardiac pacing. Administration of intravenous magnesium sulfate may be effective in the management of Torsade de Pointes. Close medical monitoring and supervision should continue until the QT interval returns to normal levels. Isoproterenol infusion into anesthetized dogs with cardiac pacing rapidly attenuates the dofetilide-induced prolongation of atrial and ventricular effective refractory periods in a dose-dependent manner. Magnesium sulfate, administered prophylactically either intravenously or orally in a dog model, was effective in the prevention of dofetilide-induced Torsade de Pointes ventricular tachycardia. Similarly, in man, intravenous magnesium sulfate may terminate Torsade de Pointes, irrespective of cause. Dofetilide capsules overdose was rare in clinical studies; there were two reported cases of dofetilide capsules overdose in the oral clinical program. One patient received very high multiples of the recommended dose (28 capsules), was treated with gastric aspiration 30 minutes later, and experienced no events. One patient inadvertently received two 500 mcg doses one hour apart and experienced ventricular fibrillation and cardiac arrest 2 hours after the second dose. In the supraventricular arrhythmia population, only 38 patients received doses greater than 500 mcg BID, all of whom received 750 mcg BID irrespective of creatinine clearance. In this very small patient population, the incidence of Torsade de Pointes was 10.5% (4/38 patients), and the incidence of new ventricular fibrillation was 2.6% (1/38 patients).
Storing it safely
Storage Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.] PROTECT FROM MOISTURE AND HUMIDITY. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.
Before you take anything new
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This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 13 May 2026. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.