Sotalol occupies a distinctive position among antiarrhythmic drugs because it combines two separate electrophysiological actions. These actions, and the adverse effect that limits its dosing, are:

• A Sodium channel block and alpha blockade, limited by hypotension
• B Adenosine receptor antagonism and beta-blockade, limited by bronchospasm
• C Calcium channel block and muscarinic antagonism, limited by bradycardia
• D Nonselective beta-blockade and IKr potassium channel block, limited by torsades de pointes ✓

Explanation

Sotalol is a racemic mixture whose d-isomer prolongs repolarization by blocking the rapid component of the delayed rectifier potassium current, while both isomers are nonselective beta-blockers. Its major dose-dependent toxicity is QT prolongation with torsades de pointes, risk rising sharply above 320 mg per day. Because it is renally cleared, dose must be reduced in renal impairment, and QT monitoring is required after initiation.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

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Written and medically reviewed by the StethoPrep medical team.