Angiotensin II receptor blockers

Amy Barreras, PharmD, and Cheryle Gurk-Turner, RPh

From the Department of Pharmacy Services, Baylor University Medical Center, Dallas, Texas.

Corresponding author: Amy Barreras, PharmD, Department of Pharmacy Services, Baylor University Medical Center, 3500 Gaston Avenue, Dallas, Texas 75246 (e-mail: AmyBarr@BaylorHealth.edu).

The angiotensin II receptor blockers (ARBs) represent a newer class of antihypertensive agents. Their mechanism of action differs from that of the angiotensin-converting enzyme (ACE) inhibitors, which also affect the renin-angiotensin system. The ARBs were developed to overcome several of the deficiencies of ACE inhibitors: competitive inhibition of ACE results in a reactive increase in renin and angiotensin I levels, which may overcome the blockade effect; ACE is a relatively nonspecific enzyme that has substrates in addition to angiotensin I, including bradykinin and other tachykinins, and thus, inhibition of ACE may result in accumulation of these substrates; production of angiotensin II can occur through non-ACE pathways as well as through the primary ACE pathway, and these alternative pathways are unaffected by ACE inhibition; specific adverse effects are associated with ACE inhibitor effects on the enzyme; and ARBs may offer more complete angiotensin II inhibition by interacting selectively with the receptor site (1). All 7 drugs in this class are approved by the Food and Drug Administration for the treatment of hypertension, either alone or in combination with other drugs. Unlabeled uses include the treatment of congestive heart failure and, for losartan and irbesartan, diabetic nephropathy (2, 3).