Randomized, controlled, parallel-group comparison of ambulatory and clinic blood pressure responses to amlodipine or enalapril during and after treatment in adult chinese patients with hypertension

Few studies have examined the relative efficacy and tolerability of antihypertensive drug classes in Chinese populations. This study compared the efficacy, tolerability, and duration of antihypertensive effect of amlodipine besylate and enalapril in Chinese patients with hypertension, including elderly patients with isolated systolic hypertension. This randomized, double-blind, double-dummy, parallel-group dose-titration study was conducted at the Department of Medicine and Therapeutics, Chinese University of Hong Kong. Chinese patients aged 18 to 80 years with primary hypertension were enrolled. After a 4-week placebo run-in period, patients were randomly assigned to receive active oral, once-daily treatment with amlodipine (5 mg) or with enalapril (5 mg) for 14 weeks. Treatment doses were titrated at weeks 4 and 8 if necessary according to blood pressure (BP) response and if the dose had been tolerated. Patients also underwent 24-hour ambulatory BP monitoring (ABPM) at the end of the placebo run-in, after the first and last doses of active treatment, and 48 hours after discontinuation of treatment to determine the duration of drug action and to mimic the effect of 2 missed doses. Eighty patients were recruited for the study (26 men, 54 women; mean [SD] age, 60.5 [11.6] years) (40 patients per group). Thirty-seven patients in each group completed the active treatment phase. Baseline trough BPs were similar: 167.7 (15.0)/94.6 (9.7) mm Hg in the amlodipine group and 168.6 (11.9)/93.4 (9.5) mm Hg in the enalapril group. After 14 weeks of treatment, amlodipine (mean [SD] final dose, 6.3 [2.3] mg) produced greater reductions than enalapril (mean [SD] final dose, 13.3 [6.6] mg) in trough BP (−20.8 [13.2]/−9.2 [9.0] vs −5.5 [14.9]/−3.2 [10.6] mm Hg, respectively; P ≤ 0.01). Most of the effect of amlodipine persisted for 72 hours after the last dose (−18.9 [14.6]/−11.1 [11.7] mm Hg), but enalapril had no significant antihypertensive effect at 72 hours (−1.3 [12.3]/−1.8 [9.1] mm Hg). Similar observations were found with ABPM recordings. Cough was reported in 5 patients (12.5%) and 13 patients (32.5%) in the amlodipine and enalapril groups, respectively, but was thought to be treatment related in only 6 patients (15.0%), all in the enalapril group. One of the patients in the enalapril group withdrew from the study because of cough, and 1 patient in the amlodipine group withdrew because of ankle edema.