Angiotensin II receptor blockers, also known as ARB blockers or angiotensin 2 receptor blockers, are drugs used to treat high blood pressure and heart failure. They do not interfere with the body's production of angiotensin. Instead, they block the effects of angiotensin, preventing the hormone from narrowing the blood vessels. By relaxing the coronary arteries, blood flow to the heart increases, blood pressure goes down and the heart's workload is reduced. Angiotensin II receptor blockers are often used in patients who cannot tolerate a common type of drugs known as ACE inhibitors.