Tikosyn

dofetilide

(doe-fet-il-ide) ,

Tikosyn

(trade name)

Classification

Therapeutic: antiarrhythmics
Pregnancy Category: C

Indications

Maintenance of normal sinus rhythm (delay in time to recurrence of atrial fibrillation/atrial flutter [AF/AFl]) in patients with AF/AFl lasting more than one week, and who have been converted to normal sinus rhythm.Conversion of AF and AFl to normal sinus rhythm.

Action

Blocks cardiac ion channels responsible for transport of potassium.
Increases monophasic action potential duration.
Increases effective refractory period.

Therapeutic effects

Prevention of recurrent AF/AFl.
Conversion of AF/AFl to normal sinus rhythm.

Pharmacokinetics

Absorption: Well absorbed (>90%) following oral administration.
Distribution: Unknown.
Metabolism and Excretion: 80% excreted by kidneys via cationic renal secretion, mostly as unchanged drug; 20% excreted as inactive metabolites; some metabolism in the liver via cytochrome P450 system (CYP3A4 isoenzyme).
Half-life: 10 hr.

Time/action profile (blood levels)

ROUTEONSETPEAKDURATION
POwithin hours2-3 hr†12-24 hr
†Steady state levels are achieved after 2–3 days

Contraindications/Precautions

Contraindicated in: Hypersensitivity;Congenital or acquired prolonged QT syndromes;Baseline QT interval or QTc of >440 msec (500 msec in patients with ventricular conduction abnormalities);Creatinine clearance <20 mL/min;Concurrent use of verapamil, cimetidine, ketoconazole, itraconazole, trimethoprim, megestrol, prochlorperazine, hydrochlorothiazide, or other QT-interval prolonging drugs; Lactation: Avoid use.
Use Cautiously in: Underlying electrolyte abnormalities (↑ risk of serious arrhythmias; correct prior to administration);Creatinine clearance 20–60 mL/min (dose ↓ recommended);Severe hepatic impairment; Obstetric: Use only when potential benefit to patient outweighs potential risk to fetus; Pediatric: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness (most frequent)
  • headache (most frequent)

Cardiovascular

  • ventricular arrhythmias (including torsade de pointes) (life-threatening)
  • chest pain (most frequent)
  • QT interval prolongation

Interactions

Drug-Drug interaction

Hydrochlorothiazide, verapamil, cimetidine, ketoconazole, itraconazole, trimethoprim, megestrol, and prochlorperazine ↑ dofetilide levels and the risk of QT interval prolongation with arrhythmias; concurrent use is contraindicated.QT interval prolonging drugs may ↑ the risk of QT interval prolongation with arrhythmias; concurrent use contraindicated.Amiloride, metformin, and triamterene may also ↑ dofetilide levels; use with caution.Inhibitors of the cytochrome P450 system (CY P450 3A4 isoenzyme) including macrolide anti-infectives, azole antifungals, protease inhibitor antiretrovirals, SSRI antidepressants, amiodarone, diltiazem, nefazodone, quinine, and zafirlukast may also ↑ blood levels and the risk of arrhythmias and concurrent use should be undertaken with caution.Should not be used concurrently with other class I or III antiarrhythmics due to ↑ risk of arrhythmias.Hypokalemia or hypomagnesemia from potassium-depleting diuretics ↑ the risk of arrhythmias; correct abnormalities prior to administration.Concurrent use of digoxin may ↑ the risk of arrhythmias.Grapefruit juice may ↑ levels; avoid concurrent use.

Route/Dosage

Dosing should be adjusted according to renal function and assessment of QT interval
Oral (Adults) Starting dose—500 mcg twice daily; maintenance dose—250 mcg twice daily (not to exceed 500 mcg twice daily).

Renal Impairment

Oral (Adults) CCr 40–60 mL/min Starting dose—250 mcg twice daily; maintenance dose—125 mcg twice daily; CCr 20– 40 mL/min Starting dose—125 mcg twice daily; maintenance dose—125 mcg once daily.

Availability

Capsules: 125 mcg, 250 mcg, 500 mcg

Nursing implications

Nursing assessment

  • Monitor ECG, pulse, and BP continuously during initiation of therapy and for at least 3 days, then periodically during therapy. Evaluate QTc prior to initiation of therapy and every 3 mo during therapy. If QTc exceeds 440 msec (500 msec in patients with ventricular conduction abnormalities), discontinue dofetilide and monitor patient until QTc returns to baseline.
  • Assess the patient’s medication history including OTC, Rx, and natural/herbal products, with emphasis on those that interact with dofetilide (see Interactions).
  • Lab Test Considerations: Creatinine clearance must be calculated for all patients prior to administration and every 3 mo during therapy.

Potential Nursing Diagnoses

Decreased cardiac output (Indications)

Implementation

  • Dolfetilide must be initiated or reinitiated in a setting that provides continuous ECG monitoring and has personnel trained in the management of serious ventricular arrhythmias and pharmacists trained to dispense dofetilide. Due to the potential for life-threatening ventricular arrhythmias, dofetilide is usually used for patients with highly symptomatic AF/AFl.
    • Patients with AF should be anticoagulated according to usual protocol prior to electrical or pharmacological cardioversion.
    • Make sure patient has an adequate supply of dofetilide prior to discharge to prevent interruption of therapy.
    • Patients should not be discharged from the hospital within 12 hr of electrical or pharmacological conversion to normal sinus rhythm.
  • Oral: Administer at the same time each day without regard to food.

Patient/Family Teaching

  • Instruct patient to take medication as directed, even if feeling well. If a dose is missed, do not double next dose. Take next dose at usual time.
  • Patient should read the patient package insert prior to initiation of therapy and reread it each time therapy is renewed. Emphasize the need for compliance with therapy, the potential for drug interactions, and the need for periodic monitoring to minimize the risk of serious arrhythmias.
  • Instruct patient or family member on how to take pulse. Advise patient to report changes in pulse rate or rhythm to health care professional.
  • May cause dizziness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
  • Advise patient to inform health care professional of medication regimen prior to treatment or surgery.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking other Rx, OTC, or herbal products.
  • Advise patient to consult health care professional immediately if they faint, become dizzy, or have fast heartbeats. If health care professional is unavailable, instruct patient to go to nearest hospital emergency department, take remaining dofetilide capsules, and show them to the doctor or nurse. If symptoms associated with altered electrolyte balance such as excessive or prolonged diarrhea, sweating, or vomiting or loss of appetite or thirst occur, health care professional should also be notified immediately.
  • Emphasize the importance of routine follow-up exams to monitor progress.

Evaluation/Desired Outcomes

  • Prevention of recurrent AF/AFl.
  • Conversion of AF/AFl to normal sinus rhythm.
    • If patients do not convert to normal sinus rhythm within 24 hr of initiation of therapy, electrical conversion should be considered.

Tikosyn®

Dofetilide Cardiology A selective potassium channel blocker for treating A Fib, to maintain normal heart rhythm and ↓ fatigue, SOB, and other Sx. See DIAMOND CHF trial.
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Then we tried anti-eurythmic drugs, and then Tikosyn, which was successful for about a year.
Patients prescribed Effexor XR who took Tikosyn by mistake could potentially have a fatal reaction, the drug maker cautioned.
At a Food and Drug Administration hearing in January, Tikosyn investigator Dr.
Comment: In trials of 996 patients, about 10% of those on 500 [mu]g of Tikosyn per day and 30% of those on 1,000 [mu]g/day converted to NSR, vs.
received approval from the FDA to market dofetilide capsules, a generic alternative to Tikosyn, an anti-arrhythmic agent used to treat irregular heartbeats, such as atrial fibrillation and atrial flutter.
Company officials note that the timing of Mayne Pharma's market approval coincided with the FDA's withdrawal of the Tikosyn Risk Evaluation and Mitigation Strategies (REMS) program, which limited the drug's availability and dispensation to certified prescribes, pharmacies and wholesalers.
At a Food and Drug Administration advisory panel hearing in January, Tikosyn investigator Dr.
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Another therapy that the company has high hopes for is Tikosyn for the treatment of atrial fibrillation.