Sustained‐Release Diltiazem: Duration of Antihypertensive Effect

The antihypertensive activity of a sustained‐release preparation of diltiazem (given each 12 hours) was assessed in 96 patients with supine diastolic blood pressure (BP) between 95 and 110 mm Hg in a multicenter, randomized, double‐blind, placebo run‐in, parallel‐group trial comparing optimally titrated doses of diltiazem and placebo. The aim was to assess the onset of action as well as the extent and variability of BP control of this formulation during the 12‐hour interval. Diltiazem was titrated from 120 mg bid to 180 mg bid as necessary to lower BP. At baseline, on the first day of titration, and at the end of 8 weeks, BP was evaluated at 0, 1, 2, 3, 4, 5, 6, 8, 10, and 12 hours after dosing. The onset of action was within 2 hours, and the effect was maintained throughout the 12‐hour period. Mean BP for the diltiazem group at baseline was 154/101 mm Hg. At week 8, BP was 148/93 mm Hg at hour “0” (P < .02 andP = .0001 for systolic and diastolic BP vs. placebo), 139/84 mm Hg at the nadir at hour 5 (P = .0001), and 149/91 mm Hg at the end of the 12‐hour period (P < .02 andP = .0001 for systolic and diastolic BP). Diltiazem was significantly more effective than placebo (P = .0001) with 50% of patients controlled to a diastolic pressure of <90 mm Hg at 7 of the 10 evaluation points, including the evaluation point of 12 hours post‐dose. There was no exaggeration of the magnitude of daily BP fluctuation nor any increase in orthostatic effect noted.