Dofetilide

INTRODUCTION

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 1 wk, and who have been converted to normal sinus rhythm. For the conversion of atrial fibrillation and atrial flutter 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.

Adverse Reactions/Side Effects

CNS: dizziness, headache. CV: VENTRICULAR ARRHYTHMIAS, chest pain, QT interval prolongation.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Although intended to treat certain arrhythmias, this drug can unmask or precipitate new arrhythmias (proarrhythmic effect). Report any rhythm disturbances or symptoms of increased arrhythmias, including palpitations, chest pain, shortness of breath, fainting, and fatigue/weakness.

• Assess dizziness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

Interventions

• Because of the risk of arrhythmias, use extreme caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (blood pressure, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

Patient/Client-Related Instruction

• Advise patient and family or caregivers about the signs of arrhythmias (see above under Examination and Evaluation), and to seek immediate medical assistance if these signs develop.

• Instruct patient and family/caregivers to report other side effects such as severe or prolonged headache or chest pain.

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.

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 (CCr) <20 mL/min; Concurrent use of verapamil or agents which inhibit the renal cation ...