Angiotensin-converting enzyme inhibitors (ACE-I) are drugs used to treat hypertension and heart failure.

In hypertension, ACE inhibitors (ACE-I) are the first-line treatment in patients below 55 years of age either alone or in combination with other antihypertensives (usually calcium channel blockers or diuretics). ACE-I blood pressure by blocking the activity of the angiotensin-II converting enzyme. In this way, ACE inhibitors decrease the workload on the heart and help improve blood flow to body organs. ACE-I are particularly advantageous in treating hypertension in patients with diabetes, coronary artery disease, and renal disease. ACE inhibitors are also indicated in the treatment of heart failure, particularly in combination with beta-blockers, aldosterone antagonists, and diuretics.

Ramipril, lisinopril, perindopril, trandolapril, and enalapril are the most commonly used ACE inhibitors in the UK.

Patients on ACE inhibitors need to monitor their blood pressure regularly. Also, GPs will usually check their kidney function by taking a blood sample about 7-10 days after starting the treatment and following each subsequent dose adjustment. ACE inhibitors may deteriorate kidney function but reducing kidney perfusion, but they are beneficial in patients with mild kidney disease. As with any other medications, ACE inhibitors should not be stopped without medical advice. Sudden withdrawal of ACE inhibitors may lead to a dangerous increase in blood pressure.

Dry cough is the most common side effect of ACE inhibitors, which may necessitate a change to angiotensin receptor blockers (ARBs), which have a very similar mode of action but without this particular side effect. Some people may experience dizziness or even fainting due to an excessive drop in blood pressure (hypotension), in which case they should take ACE inhibitors in the evening before going to bed. ACE inhibitors can rarely cause a severe allergic reaction which manifests with swelling of the face (angioedema), which requires urgent medical attention.