Comparison of valsartan and irbesartan in the treatment of mild to moderate hypertension: a randomized, open-label, crossover study

Abstract

Background: Differences in the pharmacokinetic and pharmacodynamic variables of angiotensin II receptor blockers (ARBs) have been cited as potentially important causes of differential clinical efficacy with respect to the magnitude and duration of the antihypertensive response. Objective: The goal of this study was to compare the antihypertensive efficacy of valsartan versus irbesartan using 24-hour ambulatory blood pressure monitoring (ABPM) in the treatment of mild to moderate hypertension. Methods: After a 2-week placebo washout period, outpatients of both sexes aged 31 to 60 years with mild to moderate hypertension were randomly assigned to treatment with irbesartan 150 mg or valsartan 80 mg, both administered once daily, for 4 weeks. After another 2-week placebo washout period, patients were switched to the alternate regimen for an additional 4 weeks. Patients were assessed at the end of each placebo and active treatment period. At each visit, casual blood pressure (BP) and heart rate were measured and 24-hour ABPM was performed using a portable, noninvasive, fully automatic recorder. Recordings were excluded from analysis when >10% of all readings or >1 reading per hour was missing or incorrect. Trough/peak ratio was assessed in each treatment group, and the smoothness index was determined to quantify the homogeneity of the antihypertensive effect over 24 hours. Results: Forty patients (20 men and 20 women; mean age, 51 ± 7 years) were included in the study. One patient withdrew after randomization (lost at follow-up); the results are given for 39 patients. Both valsartan and irbesartan significantly lowered 24-hour, daytime, and nighttime BP values ( P < 0.001 vs placebo) without affecting the normal BP circadian profile. No significant differences in efficacy were found between the 2 drugs. Mean values for 24-hour, daytime, and nighttime heart rate, as well as the 24-hour heart rate profile, were not significantly affected by either drug. Both drugs had a trough/peak ratio >50% (valsartan, 0.65 ± 0.72 for systolic BP [SBP] and 0.62 ± 0.55 for diastolic BP [DBP]; irbesartan, 0.57 ± 0.58 for SBP and 0.69 ± 0.54 for DBP) and a similar smoothness index (valsartan, 1.26 ± 0.31 for SBP and 1.41 ± 0.17 for DBP; irbesartan, 1.32 ± 0.43 for SBP and 1.52 ± 0.43 for DBP), which suggests that their antihypertensive effect was homogeneous throughout the 24-hour period and lasted to the end of the dosing interval. Casual BP results confirmed that valsartan and irbesartan were equally effective in reducing SBP and DBP values. Conclusions: Valsartan and irbesartan are 2 ARBs with different pharmacologic properties. Valsartan is more selective for angiotensin type 1 receptors than is irbesartan; irbesartan has a longer half-life and demonstrates insurmountable antagonism. These distinct pharmacologic properties did not appear to result in different effects on the magnitude and duration of antihypertensive efficacy.