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

BACKGROUND: Few studies have examined the relative efficacy and tolerability of antihypertensive drug classes in Chinese populations. OBJECTIVE: 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. METHODS: 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. RESULTS: 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 <or = 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.