A multicenter, randomized, double-blind study of the antihypertensive efficacy and tolerability of irbesartan in patients aged > or = 65 years with mild to moderate hypertension.

BACKGROUND: Blockade of the renin-angiotensin-aldosterone system (RAAS) is the preferred mechanism of action for controlling hypertension in select groups of patients, including those with diabetic nephropathy and heart failure. Currently, 2 classes of drugs work by blocking the RAAS, albeit by differing mechanisms: angiotensin-converting enzyme (ACE) inhibitors and angiotensin II angiotensin type 1 receptor blockers (ARBs).

OBJECTIVE: The goal of this study was to assess the comparative efficacy and tolerability of the ARB irbesartan and the ACE inhibitor enalapril in patients > or = 65 years of age with mild to moderate hypertension (sitting diastolic blood pressure [DBP], 95 to 110 mm Hg).

METHODS: Elderly (> or = 65 years of age) patients were recruited from 26 Canadian study centers for a randomized, double-blind, 8-week clinical trial. Exclusion criteria included sitting DBP >110 mm Hg or sitting systolic blood pressure (SBP) >200 mm Hg, angina pectoris, myocardial infarction, cardiac procedure, stroke, or transient ischemic attack within 6 months of randomization, as well as other preexisting or present severe medical or psychologic conditions. Patients were randomly assigned to receive a single daily dose of irbesartan 150 mg (n = 70) or enalapril 10 mg (n = 71) with treatment doses of study drugs doubled at week 4 for sitting DBP > or = 90 mm Hg. Reductions from baseline blood pressure measurements at trough (24 +/- 3 hours after the last dose of medication) were assessed for sitting DBP and sitting SBP. Comparative tolerability to study drugs was also assessed.

RESULTS: The intent-to-treat analysis demonstrated similar reductions at week 8 in both DBP and SBP for both groups. For the primary efficacy analysis of sitting DBP, there was a mean reduction from baseline of 9.6 mm Hg and 9.8 mm Hg for the irbesartan and enalapril groups, respectively (P = 0.93). The mean reduction from baseline in sitting SBP was 10.1 mm Hg and 11.6 mm Hg for the irbesartan and enalapril groups, respectively (P = 0.54). Normalization rates (sitting DBP <90 mm Hg) at week 8 did not differ between groups (52.9% in the irbesartan group and 54.9% in the enalapril group; P = 0.81). No statistical difference existed between the 2 groups with respect to serious adverse events or discontinuations due to adverse events. Irbesartan was associated with a significantly lower incidence of cough than was enalapril (4.3% vs 15.5%, respectively; P = 0.046).

CONCLUSIONS: Irbesartan is an effective and well-tolerated antihypertensive for elderly patients with mild to moderate hypertension. This study establishes that irbesartan has better tolerability than enalapril with respect to cough and suggests that irbesartan is as effective at lowering blood pressure but better tolerated than an ACE inhibitor in hypertensive patients > or = 65 years of age.