Does isradipine modified release 5 mg once daily reduce blood pressure for 24 hours?

Twelve patients with essential hypertension were randomized in a double-blind cross-over study to investigate the blood pressure BP-lowering activity of isradipine regular formulation (RF) 2.5 mg twice daily (between 7 and 8 a.m. and at approximately 6 p.m.), and isradipine modified release (MR), 5 mg once daily (between 7 and 8 a.m.). The two randomized treatment periods were separated by a placebo period. Patient compliance was similar between placebo and isradipine RF and MR treatment. As compared with placebo, isradipine RF decreased daytime BP by 10 mm Hg systolic (SBP, p < 0.001) and by 6 mm Hg diastolic (DBP, p < 0.01), and night SBP and DBP by 7 (p < 0.05) and 3 mm Hg (P = NS), respectively. Isradipine MR reduced the daytime SBP 8 mm Hg (p < 0.05) and DBP by 3 mm Hg (p = NS), and the night SBP by 1 mm Hg (p = NS) and DBP by < 1 mm Hg (P = NS). Analysis of variance showed that the interaction terms between the effects of treatment and time of day were not significant for SBP (F = 1.56, p = 0.24) or DBP (F = 1.40, p = 0.26) with isradipine RF treatment, but they were significant for SBP (F = 6.33, p = 0.03) and DBP (F = 5.12, p = 0.04) with isradipine MR treatment. Therefore, the BP-lowering effect of isradipine MR 5 mg once daily appears to weaken as the day progresses.(ABSTRACT TRUNCATED AT 250 WORDS)