Angiotensin Ii Receptor Blockers

The ARBs have very similar clinical profiles. They do, however, have different pharmacokinetic profiles, which may lead to some differences in efficacy. The newer agents irbesartan, candesartan, telmisartan, and olmesartan have longer half-lives and durations of action than the older agents losartan and valsartan (5). Twenty-four–hour blood pressure control could be more readily achievable with the newer agents. Losartan and valsartan may need to be administered twice daily in patients needing greater antihypertensive effects, whereas the agents with longer durations of action have no added benefit when administered more than once daily. Of course, a once-daily product is always preferred. Several double-blind, head-to-head comparative trials have evaluated the relative antihypertensive efficacy of the ARBs in patients with mild to moderate hypertension. The net result is that the longer-acting agents may be more effective than losartan and valsartan at providing 24-hour blood pressure control. But, as also mentioned, a metaanalysis of 43 trials comparing the antihypertensive effects of ARBs found comparable antihypertensive efficacies within the ARB class (4, 5). Whether reported differences in efficacy are clinically relevant regarding morbidity and mortality has not been determined. When evaluating differences among the ARBs, their current and future places in therapy for unlabeled uses must be considered. ARBs have been evaluated for use in heart failure, as combination therapy with ACE inhibitors and alone as standard therapy. Losartan and valsartan are the only ARBs for which studies have been completed that involved long-term follow-up with morbidity and mortality as endpoints. Neither agent can replace ACE inhibitors as first-line therapy, but both remain a rational alternative for patients unable to tolerate ACE inhibitors. Candesartan is currently being evaluated for this same use.