Irbesartan: review of pharmacology and comparative properties

The recently developed and marketed angiotensin II type 1 (AT1) receptor blockers (ARBs) have demonstrated efficacy equivalent to that of other leading classes of antihypertensive agents, with superior tolerability profiles. The specific targeting of the AT1 receptor afforded by these agents has demonstrated more complete blockade of the renin-angiotensin system than that offered by angiotensin-converting enzyme inhibitors. These data notwithstanding, differentiation within the class of ARBs has been limited. With the accumulation of additional data with ARBs, it has recently become possible to make within-class distinctions, based in large part on the individual pharmacological profiles of the ARBs. To this end, absorption, distribution, half-life, dose response and level of angiotensin II antagonism are of special note. When these properties are viewed as a group, the ARB irbesartan appears to offer advantages beyond those attained with other ARBs. Irbesartan is well absorbed, does not require biotransformation to an active metabolite to exert its antihypertensive activity, offers a large volume of distribution, has a half-life that is sufficient to allow once-daily dosing, is associated with a strong and consistent dose-response and has been demonstrated to provide a level of angiotensin II antagonism that is statistically superior to that offered by some other ARBs. These pharmacological differences may explain the clinical superiority of irbesartan compared with losartan, the first member of the ARB class. As even more data on the ARBs become available, the ability to determine the advantages of specific members of this class will be enhanced, distinctions that already have begun to come to light.