ibutilide

Ibutilide is a class III antiarrhythmic agent used in adults to achieve chemical cardioversion of atrial fibrillation or atrial flutter of recent onset. It is administered intravenously in a hospital setting with continuous ECG monitoring due to the risk of serious arrhythmias, including torsades de pointes.

Pharmacology and mechanism of action: Ibutilide prolongs the cardiac action potential and the QT interval by affecting ion channel activity, thereby increasing ventricular repolarization time and refractoriness. It primarily modulates potassium currents and can influence sodium currents, which together raise the threshold for re-entrant arrhythmias but carry a risk of proarrhythmia in susceptible individuals.

Indications and administration: The medication is indicated for chemical conversion to sinus rhythm in adults with atrial fibrillation or flutter of recent onset. It is given as an intravenous infusion over about 10 minutes. If the arrhythmia persists after this initial dose, a second 1 mg dose may be given, with a maximum total dose of 2 mg.

Contraindications and precautions: Ibutilide is contraindicated in patients with congenital or acquired long QT syndrome, torsades de pointes, or significant electrolyte disturbances that cannot be corrected (eg, severe hypokalemia or hypomagnesemia). It should be used with caution in patients on other QT-prolonging drugs, in those with decompensated heart failure, or in those with hemodynamic instability.

Adverse effects and monitoring: The most serious potential adverse effect is torsades de pointes. Other common effects include headache, dizziness, nausea, and hypotension. Continuous ECG monitoring during administration and for several hours afterward is essential, with attention to electrolyte management and readiness to treat proarrhythmia.