**Question:** ACE inhibitors are contraindicated in

A. patients with severe renal impairment
B. pregnant women
C. patients with known hypersensitivity to ACE inhibitors
D. patients with angioedema due to ACE inhibitors

**Core Concept:** ACE inhibitors are a class of medications used to treat hypertension, heart failure, and diabetic nephropathy by blocking the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor and aldosterone stimulator.

**Why the Correct Answer is Right:** ACE inhibitors are contraindicated in patients with severe renal impairment as they can worsen renal function further. In such patients, renin-angiotensin-aldosterone system (RAAS) blockade with ACE inhibitors may lead to increased vasoconstriction and decreased filtration, causing acute kidney injury.

**Why Each Wrong Option is Incorrect:**

A. Patients with severe renal impairment: As explained above, ACE inhibitors can worsen renal function, making them contraindicated in this group of patients.

B. Pregnant women: Although ACE inhibitors are generally safe during pregnancy, they can cause fetal harm and should be avoided.

C. Patients with known hypersensitivity to ACE inhibitors: These patients should be treated with alternative medications to prevent anaphylactic reactions and angioedema.

D. Patients with angioedema due to ACE inhibitors: As ACE inhibitors are the primary cause of angioedema in such cases, discontinuation of these medications is necessary to prevent life-threatening reactions.

**Clinical Pearl:** In cases of suspected angioedema due to ACE inhibitors, prompt discontinuation of the medication and initiation of alternative therapy is crucial for patient safety. Always consider the potential risks and benefits when prescribing medications to patients with comorbidities, ensuring that the benefits outweigh the potential risks.