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27 January 2011

ACE inhibitors A-Z

Angiotensin-converting enzyme (ACE) inhibitors, are vasodilators that work by preventing the formation of angiotensin II.

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Angiotensin-converting enzyme (ACE) inhibitors are vasodilators that work by preventing the formation of agiotensin II. This substance is a powerful constrictor of arteries and also causes the retention of water and salt. ACE inhibitors also cause an increase in bradykinin, a vasodilator. The end result is that blood vessels relax and blood pressure drops, reducing the workload of the heart. They are preferentially used in hypertensive patients with heart failure and kidney disease.

ACE inhibitors can improve blood flow to the kidneys, reduce protein (albumin) in the urine and prevent the progression of kidney disease.

ACE inhibitors are safe and effective drugs for hypertension treatment. These drugs have also become less expensive.

A few ACE inhibitors:

  • Captopril in Capoten
  • Perindopril in Coversyl
  • Enalapril in Renitec
  • Ramipril in Tritace
  • Lisinopril in Zestril, Zetomax

Who may benefit from using ACE inhibitors?
These drugs are very helpful in treating patients with heart failure.  This includes patients with an enlarged or dysfunctional left ventricular wall, the main pumping chamber of the heart. It can therefore be helpful after a heart attack.

Diabetics may clearly benefit from treatment with ACE inhibitors. These drugs have been shown to protect against death, heart attacks, stroke and kidney disease in diabetics. Diabetics are particularly vulnerable to kidney disease.

Compelling indications for use as anti-hypertensive drug

  • Diabetes, with or without nephropathy (kidney damage)
  • Heart failure
  • Left ventricular dysfunction, especially after a heart attack
  • Kidney disease with proteinuria

How to take ACE inhibitors (dosage)
ACE inhibitors are generally well tolerated and seldom cause sudden drops in blood pressure. Some ACE inhibitors can be taken once daily, but several on the market need to be taken twice daily, which reduces convenience.

Who should not take ACE inhibitors?
ACE inhibitors protect the kidneys of diabetics by slowing the progression of kidney failure, but in patients with severe kidney problems the potassium may rise and cause problems. In these circumstances there should be close monitoring by a specialist.

Patients using ACE inhibitors and taking potassium-sparing drugs like certain diuretics or potassium supplementation need to be carefully monitored for rises in potassium. In cardiac failure a combination of ACE inhibitors with spironolactone may be particuarly beneficial, but again careful supervision by a specialist is generally advised.

ACE inhibitors must not be used during pregnancy or when planning a pregnancy. It may cause birth defects and fetal death.

Compelling contraindications

  • Pregnancy
  • Hyperkaleamia – high blood levels of potassium
  • Bilateral renal artery stenosis – narrowing of the arteries that supply the kidneys, on both sides
  • Any history ofangio-oedema

Possible contraindications or limited value

  • Renal impairment – patients with kidney disease may retain potassium. Specialist prescription and monitoring is advised.
  • Limited value as monotherapy in African patients. Combine with thiazide diuretic or calcium channel blocker.
  • Strong allergic history because of risk of angioedema

Inform your doctor if:

  • You might be pregnant or are planning to have a baby.
  • You have kidney or liver problems.
  • You have blood vessel disease.
  • You are taking any other medication.
  • You had side-effects with previous use of ACE inhibitors, especially angio-oedema.
  • You have allergies or angioedema from any cause.

Possible side-effects
The most common adverse effect is a dry cough. It is found in approximately 10 to 20% of patients taking ACE inhibitors and may require the drug to be stopped.

Some patients develop a skin rash and others may experience a change in their sense of taste.

An acute allergic reaction called angioemdea  is a rare but life-threatening side-effect. It is more common in blacks and those with an allegic hisotory.

Can it be taken with other drugs?
Non-steroidal anti-inflammatory drugs, like indometacin, may markedly reduce the effect of ACE inhibitors and promote potassium retention and kidney failure.

If taken with potassium supplements or potassium-sparing drugs, the blood levels of potassium must be carefully monitored. Very high potassium levels can be fatal due to cardiac arrest.

Written by Dr Kathleen Coetzee, MBChB

Reviewed by Prof Brian Rayner, head of the division of nefhrology and hypertension, University of Cape Town and Groote Schuur Academic Hospital, December  2010

Read more:
Alcohol and hypertension

 
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