Clinical equivalence of once-daily administration of a modified-release formulation of isradipine and twice-daily administration of the standard formulation. Multicentre Study Group.

In a double-blind, parallel-group comparative study, once-daily administration of a modified-release formulation of isradipine (Im, n = 189) was compared with twice-daily administration of the standard formulation (Is, n = 191). Following a 3- to 5-week placebo period, patients with a sitting diastolic blood pressure (sDBP) of greater than or equal to 100 mm Hg but less than or equal to 120 mm Hg were randomized to receive either Im at 5 mg once daily or Is at 2.5 mg twice daily for 6 weeks. A double-dummy technique was used to maintain blindness and no dosage titration was made. Blood pressure was always recorded in the morning before drug administration (12 h after the previous administration of Is or 24 h after the previous administration of Im). The mean sDBP was reduced significantly (p less than 0.001) and equally in both groups, and the normalization rate (sDBP less than or equal to 90 mm Hg) was 54% with Im and 55% with Is. Adverse events were slightly less frequent overall in the patients receiving Im than Is (23 vs. 28%, respectively) as was the incidence of typical dihydropyridine side effects such as flushing and headache. The results show that once-daily administration of 5 mg of Im is as effective and better tolerated than 2.5 mg twice daily of Is while providing adequate blood pressure control at the end of the 24-h dosing interval.