Angiotensin II receptor blockers (ARBs) are medications that lower blood pressure and may be used in the treatment of high blood pressure (hypertension). A relatively new medication, they produce similar effects as angiotensin converting enzyme (ACE inhibitors but by a different mechanism.

Both medications work by affecting a substance in the body called angiotensin II. Angiotensin II signals the blood vessels to constrict or narrow. In some people, angiotensin II may cause several adverse effects in the body, including high blood pressure and an increased risk of certain heart conditions.

ACE inhibitors directly lower levels of angiotensin II in the body by preventing the conversion of inactive angiotension I to active angiotensin II. Conversely, ARBs reduce the effect of angiotensin-II by blocking it from entering angiotensin II receptors in the smooth muscles of the heart and blood vessels.

As a result of either medication, blood vessels dilate or relax, and blood pressure is reduced. Both ACE inhibitors and ARBs belong to a category of medications called vasodilators. 

ARBs are not interchangeable with ACE inhibitors. ARBs are more reliable for consistently blocking the effects of angiotensin II. However, this research has not yet translated into additional medical benefits of ARBs when compared to ACE inhibitors. ARBs are generally more expensive than ACE inhibitors, but do not cause the most common side effect of ACE inhibitors – a dry, persistent cough.

In addition, ACE inhibitors decrease the breakdown of bradykinin, a protein that has a powerful influence on the contraction of smooth muscle, such as the heart. Bradykinin has been found to cause low blood pressure (hypotension). It is not known whether the ACE inhibitor’s effects on bradykinin are helpful or harmful to the body. ARBs have no effect on bradykinin.

Currently, ARBs are primarily used in patients who are intolerant to ACE inhibitors. Although, they are not usually used as a first option, ARBs are sometimes used in addition to ACE inhibitors to treat heart failure. They are generally taken in tablet form. 

ARBs include medications such as: