What are angiotensin-converting enzyme inhibitors?

Angiotensin-converting enzyme inhibitors (ACEi) are used to treat heart conditions and some kidney problems.  They are often compared to Angiotensin Receptor Blockers (ARBs) but both have similar effects.  ACEi are the used initially despite a higher risk of side effects.  This is because ACEi are available more cheaply. Examples of ACEi include; captopril, enalipril, ramipril and trandolapril. ACEi are commonly taken orally.

How do angiotensin-converting enzyme inhibitors work?

ACEi prevent Angiotensin I being converted to Angiotensin II. Reduced Angiotensin II levels leads to less contraction of the vessel walls. ACEi also leads to reduced aldosterone release resulting in decreased fluid being retained. This leads to decreased constriction of vessel walls and other effects like excessive growth of heart cells are inhibited. Further benefits are derived from ACEi’s impact on preventing the degradation of bradykinin. Bradykinin relaxes vessel walls and so can reduce blood pressure.

What are angiotensin-converting enzyme inhibitors used for?

ACEi can be used for a variety of cardiac conditions including:

Possible Side Effects

Refer to your doctor for more information

Common side effects include:

Infrequent side effects include:

  • Rash
  • Allergic reactions
  • Build up of fluid in certain areas
  • Fever
  • Vomiting
  • Muscle cramps
  • Dry mouth

Rare side effects include:


  • Pregnancy

There is not enough evidence to conclusively prove that harm will be done to the foetus when taking ACEi- Category D.

  • Children

ACEi in children have not been studied adequately enough to confirm safe use amongst them.

  • Diuretics

Diuretics should not be taken 24-48 hours before starting treatment with an ACEi.  Diuretics can be started again after taking ACEi but they may be lower.

Can cause severe damage to the kidneys.

  • Drug interactions

Drug combinations of ACEi and an anti-inflammatory like an non-steroidal anti-inflammatory drugs (NSAID) and a thiazide diuretic increases the chance of damage to the kidneys. A diuretic and an ACEi may cause a large reduction in blood pressure. Studies have also indicated greater risk of lithium toxicity if taking lithium and an ACEi.

  •  Reduced kidney function

Extra precaution should be taken if the kidneys have reduced function.


  1. Goroll AH Angiotensin-Converting Enzyme Inhibitors versus Angiotensin II Receptor Blockers for Treatment of Essential Hypertension In: Goroll AH and Mulley AG, editors. Primary Care Medicine USA: Lippincott Company;2008
  2. Chapter 2- Cardiovascular system In: Richards D, Aronson J, editors. Oxford Handbook of Practical Drug Therapy. UK: Oxford University Press; 2005
  3. Captopril In: Donohoo E editor MIMS Online.[online] MIMS Australia Pty Ltd 2003. Available from: URL: http://www.mims.com.au
  4. Fisher NDL and Williams GH Section 4- Vascular Disease, Part 8 Disorders of the Cardiovascular System In: Kasper DL, Fauci AS et al. editors Harrison’s Principles of Internal Medicine USA: McGraw Hill; 2005
  5. Chapter 6 – Cardiovascular Drugs, 6.4 Antihypertensives, 6.4.4 ACE Inhibitors In: Australian Medicines Handbook. Australia: Australian Medicines Handbook Pty. Ltd.; 2007

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