Comparison of equal-weight oral dosages of verapamil hydrochloride and diltiazem hydrochloride in patients with mild to moderate hypertension.

The clinical efficacy, safety, and tolerability of oral verapamil and diltiazem, at total daily dosages of equal weight, were evaluated in a placebo-controlled, double-blind crossover study. Thirty-six ambulatory patients with chronic, stable, mild to moderate hypertension (supine diastolic blood pressure of 94-116 mm Hg) received a dosage of either verapamil or diltiazem 80 mg t.i.d. as the hydrochloride salt for one week after an antihypertensive-drug washout period. Each then received 120 mg of the same drug t.i.d. for one week. After another two-week washout period, the patients were crossed over to the other drug. Each patient had a 12-lead electrocardiogram and measurement of supine and standing blood pressure weekly. In the 32 patients completing the study, low-dose verapamil reduced supine diastolic blood pressure (DBP) from a mean of 101.5 +/- 5.2 to 95.3 +/- 9.5 mm Hg; high dose verapamil reduced DBP to 90.9 +/- 7.4 mm Hg. Standing DBP was reduced to a similar degree. Diltiazem showed an almost identical effect: Supine DBP was reduced from a mean of 101.7 +/- 5.3 to 94.0 +/- 10.1 mm Hg with the low dose and to 91.0 +/- 8.6 mm Hg with the high dose, with similar effects on standing DBP. The high dose of both drugs significantly increased the QTc interval, and both doses of diltiazem significantly increased the PR interval compared with baseline. Both drugs exhibited consistent efficacy with minimal adverse effects. The electrophysiologic safety profile of verapamil was superior to that of diltiazem.