ACE-inhibitors had brought about a very significant development in the treatment of hypertension, especially in cases with the complication of cardiac failure. But, it has been found that the target of inactivating the enzyme (Dipeptidil carboxypeptidase) responsible for the conversion of Angiotensin j to Angiotensin II is not strictly specific. The natural breakdown of plasma ‘bradykinin’ by the ACE is also likely to be inhibited. As a consequence, the ACE-inhibitor drugs are likely to cause accumulation of ‘bradykinin’ in the circulating blood. The possible side-effects of such drugs (e.g.. cough and sometimes the more serious one like angio-odema) have been attributed to the rise in the level of serum ‘bradykinin’. Sustained research to overcome this inherent drawback of ACE- inhibitors has finally led to the discovery of the Angiotensin II-receptor blocking drugs.
Angiotension II-receptor Antagonist (ARBs)have already been approved by the FDA in USA. These are ‘imidazole’ compounds. So far few different drugs belonging to this group are available overseas. These are ‘Losartan’, ‘Valsartan’, ‘Candesartan’, Eprosartan’, ‘Irbesartan’, ‘Telmisartan’. Losartan is now avilable in India under various brand names (e.g., ‘Losacar’, Tozar”). Such drugs can be advantageously used in hypertension patients intolerant to the ACE-inhibitors with the complaint of persistent cough as a side-effect. The ARBs as well as the ACE-inhibitors are contra-indicated during pregnancy.
Possible side-effects are – hypotensive symptoms (due to hypovalaemia of circulatory blood, especially in those taking Diuretic drugs also), hypokalemia or lowened blood potassium level and sometimes allergie skin rashes. It is desirable that such drugs should be pescribed by well- informed experienced physicians only.