Comparison of monotherapy with irbesartan 150 mg or amlodipine 5 mg for treatment of mild-to-moderate hypertension.

OBJECTIVE. The primary objective of this study was to compare the antihypertensive efficacy of the angiotensin II receptor blocker irbesartan 150 mg and the calcium channel blocker amlodipine 5 mg in the treatment of patients with seated diastolic blood pressure (DBP) 95-110 mmHg. DESIGN. Multicentre, randomised, double-blind, comparative pilot study. METHODS. Subjects were 18-65 years of age, with DBP 95-110 mmHg, and of non-African American origin. Following a three week, single-blind, placebo lead-in period, 181 subjects were randomised in a 1:1 ratio to receive once-daily irbesartan 150 mg (n=89) or amlodipine 5 mg (n=92) for four weeks. Trough (24+/-3 hours post-dosing) BP measurements were obtained at baseline and at Weeks 2 and 4 under standardised, controlled conditions. Response was defined as DBP <90 mmHg or a reduction from baseline of 10 mmHg. RESULTS. After four weeks of treatment, the mean (+/-SE) decrease from baseline in DBP was 9.4+/-0.6 mmHg in the irbesartan group vs. 9.6+/-0.6 mmHg in the amlodipine group (p=0.806). The mean decrease from baseline in seated systolic BP was 12.2+/-1.0 mmHg in the irbesartan group vs. 12.0+/-1.0 mmHg in the amlodipine group (p=0.885). Overall, 62% of subjects in the irbesartan group and 63% in the amlodipine group had a response (p=0.609), and 54% and 56% of patients (p=0.596), respectively, had their DBP normalised (<90 mmHg). Adverse events were reported by 21.3% of patients receiving irbesartan and 20.7% receiving amlodipine. Conclusions. Irbesartan 150 mg demonstrated comparable efficacy to amlodipine 5 mg, thereby confirming its value as an antihypertensive treatment option in non-African American patients with DBP 95-110 mmHg.