Angiotensin II receptor blockers help relax your blood vessels. Doing so lowers your blood pressure and makes it easier for your heart to pump blood.

Angiotensin II is a natural substance in your body that affects your cardiovascular system in many ways, such as by narrowing your blood vessels. This narrowing can increase your blood pressure and force your heart to work harder. Angiotensin II also stimulates the release of aldosterone, a hormone that increases your body's retention of sodium and water, which can lead to increased blood pressure. It can also thicken and stiffen the walls of your blood vessels and heart.

Angiotensin II receptor blockers block the action of angiotensin II. That allows blood vessels to widen (dilate). Angiotensin II receptor blockers are similar to angiotensin-converting enzyme (ACE) inhibitors. But while angiotensin II receptor blockers block the action of angiotensin II, ACE inhibitors block the actual production of angiotensin II.

Numerous angiotensin II receptor blockers are available. Which one is best for you depends on your health and the condition being treated.

Examples of angiotensin II receptor blockers include:

• Candesartan (Atacand)
• Irbesartan (Avapro)
• Losartan (Cozaar)
• Valsartan (Diovan)

Doctors prescribe these drugs to prevent, treat or improve symptoms in a variety of conditions, such as:

• High blood pressure
• Heart failure
• Kidney failure in diabetes
• Chronic kidney diseases
• Scleroderma

Side effects of angiotensin II receptor blockers may include headache, dizziness, lightheadedness, nasal congestion, back and leg pain, and diarrhea. Rare but more serious side effects include kidney failure, liver failure, allergic reaction, a drop in white blood cells and localized swelling of tissues (angioedema).

Because angiotensin II receptor blockers can cause birth defects, don't take them if you're pregnant or plan to become pregnant.