**Question:** Cough and angioedema in a patient receiving ACE inhibitors is due to

A. Angiotensin II
B. Angiotensin I
C. Bradykinin
D. Other medications

**Core Concept:** ACE inhibitors (Angiotensin-Converting Enzyme inhibitors) are a class of medications primarily used for the treatment of hypertension (high blood pressure) and congestive heart failure. ACE inhibitors work by blocking the conversion of angiotensin I to angiotensin II, which helps to reduce blood pressure and improve heart function.

**Why the Correct Answer is Right:** Cough and angioedema are adverse reactions commonly associated with ACE inhibitors. These reactions occur due to the inhibition of ACE, which results in increased levels of angiotensin II. Angiotensin II is a potent vasoconstrictor, causing airway smooth muscle constriction and increased mucus production, leading to the cough. Additionally, angiotensin II plays a role in the activation of the kallikrein-kinin system, which results in the release of bradykinin. Bradykinin is a potent vasodilator and pro-inflammatory mediator, contributing to the edema and swelling seen in angioedema.

**Why Each Wrong Option is Incorrect:**

A. Angiotensin II is not the correct answer, as it is the result, not the cause, of the cough and angioedema. Inhibiting ACE leads to increased angiotensin II levels, exacerbating the adverse reactions.

B. Angiotensin I is a precursor to angiotensin II and is not directly responsible for the cough and angioedema. The correct answer is the conversion of angiotensin I to angiotensin II, which is blocked by ACE inhibitors, leading to the observed symptoms.

C. Bradykinin is a potent vasodilator and pro-inflammatory mediator, involved in the pathophysiology of angioedema. However, it is not the cause of cough and angioedema in this context. The problem lies with the inhibition of ACE, leading to increased angiotensin II levels, which then causes the adverse reactions.

D. Other medications are not specifically mentioned as causing cough and angioedema. In this scenario, the adverse reactions are directly attributed to the inhibition of ACE and increased angiotensin II levels.

**Clinical Pearls:**

1. Cough and angioedema are important side effects to recognize and report when prescribing ACE inhibitors.
2. ACE inhibitors are generally well-tolerated and have a favorable risk-benefit ratio, but it is crucial to be aware of these potential side effects.
3. In case of suspected adverse reactions, consider discontinuing the ACE inhibitor therapy and switch to an alternative antihypertensive medication to prevent further complications.