Angiotensin converting enzyme inhibitors, or ACE inhibitors, are a class of oral medications that act primarily through blockade of the angiotensin converting enzyme. This enzyme converts angiotensin I to angiotensin II. Angiotensin II causes vasoconstriction that increases afterload, thus increasing systemic blood pressure. Angiotensin contributes to the production of aldosterone, which normally acts to retain sodium and water.

• A non-productive cough is common with ACE inhibitors and is due to increased bradykinin in the lungs. This cough does not occur with angiotensin receptor blockers (ARBs).
• Angioedema is a life-threatening reaction that is relatively common with ACE inhibitors.
• A rash is common with ACE inhibitors.
• Hypotension can occur with ACE inhibitors, causing dizziness and weakness.
• Hyperkalemia can occur due to the aldosterone inhibition.
• Renal failure can occur due to efferent arteriolar vasodilation.