Losartan - The first of a new class of antihypertensive drugs

During the past few years, angiotensin-converting enzyme (ACE) inhibitors have become increasingly popular in the treatment of hypertension and heart failure, but they have some limitations, in particular the side effect of a dry cough which develops in up to 50% of Oriental patients and is thought to be caused by the potentiation of bradykinin by kininase II inhibition. This annoying dry cough may result in discontinuation of ACE inhibitors in many patients with heart failure as well as hypertension, although definitive studies have shown that the mortality in heart failure can be reduced with ACE inhibitor treatment. Recently, a new class of antihypertensive drugs, namely angiotensin II type 1 (AT₁) receptor antagonists, has been approved; the first available one is losartan. Unlike ACE inhibitors, the angiotensin II receptor antagonists act at the receptor level, specifically blocking the effects of angiotensin II, the main effector peptide of the renin-angiotensin system. Therefore, theoretically, angiotensin II antagonists may provide greater efficacy than ACE inhibitors. Additionally, angiotensin II receptor antagonists apparently do not potentiate bradykinin, thus avoiding the side effect of the dry cough characteristic of ACE inhibitors. Conversely, angiotensin II receptor antagonists may lack some of the possible beneficial effects of bradykinin potentiation. Preliminary studies all have shown beneficial effects using losartan in various conditions such as hypertension, heart failure, nephrotic syndrome with dyslipidemia and chronic renal failure. The question whether angiotensin II receptor antagonists represent an advance over ACE inhibitors has not been resolved, and the information provided here represents a review of the present clinical studies. ACE inhibitors have been used for many years and a number of large clinical trials have clearly demonstrated their value. Comparable studies are required for angiotensin II receptor antagonists before a definitive conclusion can be drawn.