Usefulness of d, I sotalol for suppression of chronic ventricular arrhythmias. Sotalol is a unique beta-blocking drug, possessing significant class III antiarrhythmic activity. The efficacy and safety of 2 doses of sotalol (320 and 640 mg/day, divided in 2 doses) were compared to placebo in a 6-week randomized, double-blind, multicenter study of 114 patients with chronic ventricular premature complexes (VPCs) at frequencies of greater than or equal to 30/hour. Sotalol significantly reduced VPCs in patients receiving both low (n = 38) and high (n = 39) doses, compared with patients (n = 37) receiving placebo (by 75 and 88%, respectively, vs 10%; p less than 0.001, sotalol vs placebo; p less than 0.05, high vs low dose). The individual efficacy criterion (greater than or equal to 75% VPC reduction) was achieved in 34% of low-dose and 71% of high-dose sotalol versus 6% of placebo-treated patients (p less than 0.003, sotalol vs placebo; p = 0.007, high vs low dose). Repetitive beats were suppressed 25% by placebo (difference not significant), 80% by low-dose (p less than 0.003) and 78% by high-dose sotalol (p less than 0.005). Sotalol decreased heart rate (by 24 to 25%, p less than 0.001) and increased PR (by 4 to 6%, p less than 0.001) and corrected JT intervals (by 12 to 13%, p less than 0.001), but did not change ejection fraction. Proarrhythmia (nonfatal) occurred in 3 sotalol and in 2 placebo patients. Nine discontinued therapy because of adverse effects (1 low dose and 8 high dose, p less than 0.02). In summary, sotalol is an efficacious antiarrhythmic drug for VPC suppression; in lower doses, it is somewhat less effective but better tolerated. 