Angiotensin is a short peptide hormone that causes constriction of the efferent arteriole at the glomerular leading to the increased glomerular filtration pressure. This can maintain glomerular filtration when renal blood flow drops (low blood pressure, renal artery stenosis) but drugs may paralyse this reflex. Angiotensin also has effects on many other cells and it is likely that its effects depend on these too.
Angiotensin converting enzyme inhibitors (ACE inhibitors)
Excellent agents for hypertension in renal disease, and for proteinuria-associated renal disease:
- Effective with a low incidence of adverse symptoms
- Reduce proteinuria, regardless of cause
- Proven protective effect on renal function in renal disease with proteinuria
- Hypotensive effect potentiated by sodium restriction and diuretics
Most evidence for these benefits has come from trials in which ACE inhibitors were used at maximum or near-maximum doses.
Problems
1. Cause a dry cough in some recipients
2. Can cause hyperkalaemia; especially
- in combination with other drugs (e.g. potassium-sparing diuretics)
- in patients with renal impairment
3. Can cause acute renal failure in presence of renal artery stenosis
- if renal artery stenosis is bilateral or to a single kidney
- more likely if combined with diuretic therapy
4. Predispose to acute renal failure if patient becomes dehydrated or infected or cardiac output or blood pressure drop.
Choice of drug
Some are effective when given once daily. Some may be less likely to cause first-dose hypotension. However most effects are shared by all drugs in the class. Captopril was the prototype, but it needs to be given two or three times daily and has some additional side effects.
Angiotensin II receptor type I antagonists (ARBs)
Angiotensin receptor blockers (ARBs) have similar effects and side-effects to ACE inhibitors, except that they do not cause cough. They are first-choice alternatives if ACE inhibitor-induced cough occurs, but are otherwise probably broadly comparable. They are usually more expensive. In trials in type II diabetes irbesartan and losartan were shown to be superior to other hypotensive agents, but ACE inhibitors were not directly compared.
How to start an ACE inhibitor or ARB
Further info
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