What is hypertension? Hypertension is a medical condition in which blood pressure in the arteries is high. (Nordqvist 2013) Hypertension is commonly known as high blood pressure. If hypertension is left untreated, it can lead to serious health problems such as stroke and heart failure. In order to treat hypertension, the drug Losartan is used. Losartan is an angiotensin II receptor antagonist (AIIRA). In other words, it can also be called an angiotensin receptor blocker. (Allen 2012) There are generally two categories of hypertension, primary hypertension and secondary hypertension. The causes of primary hypertension are generally unknown and it develops gradually over years. As for secondary hypertension, the causes are mainly underlying other health problems and it develops suddenly. (Healthline Editorial Team 2013) First, hypertension may be linked to the renin-angiotensin-aldosterone system (RAAS). Renin is an enzyme secreted primarily via the juxtaglomerular apparatus of the kidney when sodium retention and water retention are reduced in the blood. (Beevers, Lip and O'Brien 2001) Renin will bind to a substrate which is angiotensinogen and form angiotensin I which is an inactive peptide. (Foëx and Sear 2004) After this, angiotensin I will be rapidly converted into an active peptide, angiotensin II, by angiotensin converting enzyme (ACE) in the lungs. As a result, vasoconstriction occurs due to the presence of angiotensin II, which increases blood pressure. Additionally, angiotensin II can stimulate the release of aldosterone from the adrenal glands. Aldosterone secretion increases blood pressure by reabsorbing sodium salts and water to increase sodium and water retention. (Beevers, Lip and O'Brien 2001)B...... middle of paper ......t cannot be ignored. Uncontrollable hypertension can be very dangerous as it can lead to many other diseases such as heart failure, stroke and diabetes. Therefore, people should have a regular check-up for hypertension. As noted above, the pathophysiology of hypertension is due to the renin-angiotensin-aldosterone system. Others, such as cardiac output, peripheral resistance, and endothelial dysfunction, may also be related to the pathophysiology of hypertension. Medicines like losartan are used to treat hypertension. It acts on the renin-angiotensin-aldosterone system by competing with angiotensin II to bind to AT1 receptors and thus stopping the production of aldosterone which would increase blood pressure. Finally, this medicine should be taken accordingly, with the advice of doctors and pharmacists because some people may experience side effects and allergic reactions...