Sotalol is a drug used in individuals with rhythm disturbances (cardiac arrhythmias) of the heart, and to treat hypertension in some individuals. It is a non-selective competitive β-adrenergic receptor blocker (beta blocker) that also exhibits Class III antiarrhythmic properties by its inhibition of potassium channels. Because of this dual action, Sotalol prolongs both the PR interval and the QT interval. Originally discovered around 1960, sotalol became widely used first as a β-blocker in the 1980s, and its function as an antiarrhythmic drug was discovered soon after. Due to the dual action of sotalol, it is often used preferentially to other β-blockers as treatment for both ventricular fibrillation and ventricular tachycardia.