Antihypertensive effects of mibefradil: a double-blind comparison with diltiazem CD

Mibefradil is the first compound of a new class of calcium antagonists with a unique chemical structure and mechanism of action. This trial compared mibefradil with diltiazem CD, a widely prescribed calcium antagonist for the treatment of hypertension.

In all, 201 patients with uncomplicated, mild-to-moderate essential hypertension with a baseline sitting diastolic blood pressure (SDBP) of > or = 95 and < or = 114 mmHg were evenly randomized to receive either mibefradil (100 mg) or diltiazem CD (360 mg) daily for 12 weeks. To determine whether antihypertensive effects persisted after 12 weeks, patients then entered a 4-week withdrawal period during which they remained on active treatment or were switched to placebo.

Efficacy variables were the changes from baseline in SDBP to the end of the treatment period (Week 12) and during the randomized withdrawal period (Week 16). At Week 12, the reduction from baseline in SDBP at trough was significantly greater (p < 0.001) in the mibefradil group (-14.0 +/- 7.8 mmHg) than in the diltiazem CD group (-9.5 +/- 7.5 mmHg). Significantly more patients (72%) on mibefradil achieved SDBP normalization by Week 12 than did patients on diltiazem (51%) (p < 0.01). Patients maintained on mibefradil or diltiazem CD during the withdrawal period had a significantly larger reduction in trough SDBP at Week 16 than those switched to placebo. The incidence of side effects was similar in both treatment groups.

Once-daily mibefradil was equally well tolerated as diltiazem CD, but was more effective in lowering blood pressure at the doses studied than the extended-release formulation of diltiazem.