Dose-ranging study of a new, once-daily diltiazem formulation for patients with stable angina

A double-blind safety and efficacy dose-ranging study was conducted with a new, once-daily, extended-release (XR) diltiazem hydrochloride formulation (Dilacor XR, Rhône-Poulenc Rorer, Collegeville, PA) in 189 patients with chronic stable angina pectoris. After a 2-week placebo lead-in phase, the patients were randomly assigned to 1 of 4 once-daily, fixed-dose treatment groups: placebo, XR diltiazem 120 mg, 240 mg, or 480 mg. Extended-release diltiazem, at 240-mg and 480-mg once-daily doses, significantly improved (P < .05) total exercise time during treadmill exercise tolerance testing after 2 weeks of treatment when assessed 24 hours after the previous dose. These increasing doses of XR diltiazem were associated with incremental improvements in exercise tolerance. Outpatient function, as assessed by frequency of anginal attacks, nitroglycerin use, and ambulatory electrocardiogram (Holter, Scole Engineering Culver City, CA) monitoring of ischemic events, was also improved by XR diltiazem. This extended-release diltiazem formulation can be clinically titrated within the 120- to 480-mg dosing range, permitting effective once-daily administration for treating chronic stable angina.