Angiotensin receptor antagonists and ACE inhibitors.

BACKGROUND

ACE inhibitors are valuable and effective drugs in the treatment of hypertension, heart failure, myocardial infarction and nephropathy. Angiotensin receptor antagonists, which have recently been introduced into clinical practice, have the potential to replace ACE inhibitor therapy in many patients.

OBJECTIVE

To review the mechanisms of action, indications and side effects of ACE inhibitors and angiotensin receptor antagonists and to highlight similarities and differences between the two drug classes.

DISCUSSION

Angiotensin receptor antagonists have the theoretical advantage of being more effective in blocking the effects of angiotensin II at angiotensin type I receptors. The potential disadvantage of not potentiating bradykinin may be compensated by the unopposed action of angiotensin II on vascular angiotensin type II receptors, which appear to mediate similar beneficial cardiovascular effects to bradykinin. Angiotensin II receptor antagonists have a lower incidence of adverse effects than ACE inhibitors as they do not produce cough and appear much less likely to produce angioedema. Although ACE inhibitors are the most commonly prescribed antihypertensive drug class in Australia, they are underused for the treatment of heart failure and left ventricular dysfunction following myocardial infarction. Angiotensin receptor antagonists may become alternative therapies to ACE inhibitors in these disorders. However, at present they are only indicated for the treatment of hypertension.