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

Background: Differences in the pharmacokinetic and pharmacodynamic variable s of angiotensin II receptor blockers (ARBs) have been cited as potentially important causes of differential clinical efficacy with respect to the mag nitude and duration of the antihypertensive response. Objective: The goal of this study was to compare the antihypertensive effic acy 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 a ged 31 to 60 years with mild to moderate hypertension mere randomly assigne d to treatment with irbesartan 150 mg or valsartan 80 mg, both administered once daily, for 4 weeks. After another a-week placebo washout period, pati ents were switched to the alternate regimen for an additional 4 weeks. Pati ents 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 r ecorder. Recordings were excluded from analysis when >10% of all readings o r >1 reading per hour was missing or incorrect. Trough/peak ratio was asses sed in each treatment group, and the smoothness index was determined to qua ntify the homogeneity of the antihypertensive effect over 24 hours. Results: Forty patients (20 men and 20 women; mean age, 51 +/- 7 years) wer e included in the study. One patient withdrew after randomization (lost at follow-up); the results are given for 39 patients. Both valsartan and irbes artan significantly lowered 24-hour, daytime, and nighttime BP values (P < 0.001 vs placebo) without affecting the normal BP circadian profile. No sig nificant differences in efficacy were found between the 2 drugs. Mean value s for 24-hour, daytime, and nighttime heart rate, as well as the 24-hour he art rate profile, were not significantly affected by either drug. Both drug s had a trough/peak ratio >50% (valsartan, 0.65 +/- 0.72 for systolic BP [S BP] and 0.62 +/- 0.55 for diastolic BP [DBP]; irbesartan, 0.57 +/- 0.58 for SEP and 0.69 +/- 0.54 for DBP) and a similar smoothness index (valsartan, 1.26 +/- 0.31 for SEP and 1.41 +/- 0.17 for DBP; irbesartan, 1.32 +/- 0.43 for SEP and 1.52 +/- 0.43 for DBP), which suggests that their antihypertens ive 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 mere equally effective in reducing SEP and DBP values. Conclusions: Valsartan and irbesartan are 2 ARBs with different pharmacolog ic properties. Valsartan is more selective for angiotensin type I receptors than is irbesartan; irbesartan has a longer half-life and demonstrates ins urmountable antagonism. These distinct pharmacologic properties did not app ear to result in different effects on the magnitude and duration of antihyp ertensive efficacy.