Are there differences among angiotensin receptor blockers?

Pharmacologic effects of specific drugs are frequently attributed to their therapeutic class because all agents within a particular class have the same mechanism of action. Because "head-to-head" comparisons in trials are rare, any differentiation between drugs of the same class is usually limited to comparisons of their pharmacokinetic profiles, and it is usually assumed that most of the drugs in a therapeutic class have similar efficacies. Two recent randomized clinical trials demonstrated that the antihypertensive agents irbesartan and losartan, both angiotensin receptor blockers, are not equally effective in reducing blood pressure among patients with hypertension. In both a fixed-dose trial and a titration-protocol trial, patients treated with irbesartan achieved a greater reduction in blood pressure than did those treated with losartan. The response rate was also higher among patients treated with irbesartan. Therefore, irbesartan, used either alone or as a component of response-based combination therapy with a diuretic, is a more potent antihypertensive agent than losartan. These results and the previously published pharmacologic profiles of these drugs demonstrate that angiotensin receptor blockers are, like many other classes of antihypertensive agents, more different than alike.