Isradipine twice daily lowers blood pressure over 24 H.

The objective of this study was to compare the effects of isradipine and placebo on blood pressure (BP) at the end of the dosing interval ('trough'). Following a three-week placebo period, 187 patients who had previously shown a response to treatment with isradipine (based on office BP measurements) were randomized to double-blind treatment with 2.5 mg isradipine twice daily or placebo for six weeks. Four of these patients withdrew from the study during the double-blind phase because of adverse events (one taking isradipine and three taking placebo). Blood pressure during the double-blind study was always measured 12 h after drug administration (trough values). The rate of normalization [defined as diastolic BP (DBP) less than or equal to 90 mm Hg] was 52/96 (54%) in the isradipine-treated group compared with 30/87 (33%) in the placebo group. A further 12/96 (12%) patients taking isradipine showed a fall in DBP of greater than or equal to 10 mm Hg, although their DBP was still not less than 90 mm Hg, compared with 5/87 (6%) patients receiving placebo. This difference was statistically significant (P = .003). Thus, isradipine in a dose of 2.5 mg twice daily lowers blood pressure over 24 h.