💊 ACE Inhibitors

Angiotensin-converting enzyme (ACE) inhibitors are a class of cardiovascular medications primarily used to treat hypertension and heart failure. They are a cornerstone in the management of many chronic cardiovascular conditions.

ACE inhibitors block the enzyme responsible for converting angiotensin I to angiotensin II. This reduces levels of angiotensin II, a potent vasoconstrictor, and decreases aldosterone secretion, leading to reduced sodium and water retention. They also inhibit the breakdown of bradykinin, a vasodilator, contributing to their hypotensive effect.

ACE inhibitors are widely used for the management of essential hypertension, particularly in patients with co-existing conditions like diabetes or chronic kidney disease. They are crucial in the treatment of heart failure with reduced ejection fraction, improving symptoms and prognosis. Post-myocardial infarction, they help prevent ventricular remodelling and reduce mortality. They also have a role in diabetic nephropathy to slow disease progression.

Absolute contraindications include a history of angioedema related to previous ACE inhibitor use, bilateral renal artery stenosis, and pregnancy. They should be used with caution in patients with severe aortic stenosis or hypertrophic obstructive cardiomyopathy due to the risk of precipitating hypotension. Avoid in patients with significant hyperkalaemia.

The most common side effect is a persistent dry cough, thought to be due to bradykinin accumulation. First-dose hypotension can occur, especially in volume-depleted patients. Hyperkalaemia is a significant risk, particularly in patients with renal impairment or those taking potassium-sparing diuretics. Renal impairment can worsen, and angioedema, though rare, is a life-threatening complication.

Before initiating treatment, renal function (urea, creatinine, eGFR) and electrolytes (especially potassium) should be checked. These parameters should be re-checked within 1-2 weeks of starting or increasing the dose, and then regularly thereafter (e.g., annually) or if the patient becomes unwell. Blood pressure should be monitored regularly.

Always check for a history of angioedema or severe allergic reactions. Be mindful of drug interactions, particularly with NSAIDs (risk of acute kidney injury) and potassium-sparing diuretics (risk of hyperkalaemia). Counsel patients about the possibility of a dry cough, first-dose hypotension, and the importance of regular blood tests. Advise women of childbearing potential about the risks in pregnancy.

High-yield topics include the mechanism of action, the classic side effects (cough, angioedema, hyperkalaemia), and their role in heart failure and hypertension. Remember the contraindication in pregnancy and bilateral renal artery stenosis. The 'first-dose hypotension' phenomenon is also frequently tested.

SBAs often test the classic side effects like dry cough or angioedema. Questions may present a patient with worsening renal function or hyperkalaemia after starting an ACE inhibitor, asking for the next best step. Another common scenario involves a pregnant patient, highlighting the contraindication in pregnancy.