Angiotensin-converting enzyme inhibitors in hypertension: a review

Angiotensin-converting enzyme (ACE) inhibitors are a new class of drugs, whose main indications are the treatment of hypertension and of heart failure. Data obtained with captopril, the first orally active ACE inhibitor, affords an understanding of the rationale of their therapeutic use based on the knowledge of their mechanisms of action, efficacy, contraindications and precautions, dosage and frequency of administration, side-effects, interactions and advantages. ACE inhibitors appear to exert their haemodynamic effect mainly by inhibiting the renin-angiotensin-aldosterone system, but also by modulating sympathetic nervous system activity and by increasing prostaglandin synthesis. Therefore they act both on vasoconstrictor and volume factors, since they cause vasodilation (the main effect) and mild natriuresis without affecting the heart rate and contractility and, probably, favourably influencing renal, coronary and cerebral circulation. So far it appears that ACE inhibitors can be usefully employed in the treatment of heart failure, in which they reduce both pre- and after-load, and mainly of hypertension. In the past captopril has been used to treat only severe and or resistant hypertension and some secondary forms, like renal parenchymal and renovascular hypertension, but now it seems that captopril is useful also to treat mild to moderate essential hypertension. Their efficacy in reducing blood pressure is similar to that of thiazide diuretics and of beta-blockers, the two drugs now considered of first choice and they exert their hypotensive action without the development of pseudotolerance or tolerance. ACE inhibitors seem, at the moment, contraindicated in pregnancy and in hyperkalaemic syndromes and must be used with caution in patients with collagen disease (mainly associated with renal failure), with severe bilateral renal artery stenosis (and with severe artery stenosis of a solitary kidney) and with severe sodium depletion. It is now established that captopril has a flat dose response curve and that it must be given (twice daily) at a dose not exceeding 150 mg/day. The same pharmacological approach must be used with future ACE inhibitors in order to establish the right posology and the frequency of administration. In this respect enalapril seems to be a promising ACE inhibitor with a prolonged action (at least 24 hours). The exact posology of ACE inhibitors might be crucial, since it has been shown that the side-effects of captopril (skin rashes, fever, taste disturbances, proteinuria and neutropenia) are dose dependent.(ABSTRACT TRUNCATED AT 400 WORDS)