The angiotensin receptor blockers (ARBs), also called angiotensin (AT I) receptor antagonists or sartans, are a group of drugs that act by blocking the effects of angiotensin II (Ang II) in the body. Their structure is similar to Ang II and they bind to Ang II receptors as inhibitors. Angiotensin receptor blockers are widely used drugs with the main indications being hypertension, chronic heart failure, secondary stroke prevention, high-risk patients for atherosclerosis and nephropathy and more recently, ischemic heart disease. With the introduction of angiotensin converting enzyme (ACE) inhibitors, it was confirmed that Ang II plays an important role in regulating blood pressure, and electrolyte and fluid balance. Blood pressure and fluid and electrolyte homeostasis is regulated by the renin-angiotensin-aldosterone-system. Renin, an enzyme released from the kidneys, converts the inactive plasma protein angiotensinogen into Ang I. Then Ang I is converted to Ang II with ACE. The AT I receptor mediates Ang II to cause increased cardiac contractility, sodium reabsorption and vasoconstriction which all lead to increased blood pressure. By blocking AT I receptors, ARBs lead to lower blood pressure.