Following statements are true/false about drugs affecting renin angiotensin aldosterone system?1. Aliskiren acts by inhibiting the secretion of renin2. Enalapril can cause cough and angioedema3. Losartan inhibits the formation of angiotensin II4. Epleronone causes gynaecomastia as an adverse effect5. Sampatrilat has additional inhibitory activity on neprilysin apart from inhibitory effect on ACE.

**Core Concept**
The renin-angiotensin-aldosterone system (RAAS) is a crucial regulator of blood pressure and fluid balance, involving **renin**, **angiotensin-converting enzyme (ACE)**, **angiotensin II**, and **aldosterone**. Drugs targeting this system are used to manage hypertension and heart failure.

**Why the Correct Answer is Right**
Aliskiren is a direct renin inhibitor, which means it directly inhibits the action of **renin**, an enzyme critical for the initiation of the RAAS cascade. Enalapril, an ACE inhibitor, can cause cough and angioedema due to the accumulation of **bradykinin**. Losartan is an angiotensin II receptor antagonist, not an inhibitor of angiotensin II formation. Eplerenone is a selective **aldosterone receptor antagonist** with less likelihood of causing gynaecomastia compared to spironolactone. Sampatrilat has a dual inhibitory effect on both **ACE** and **neprilysin**, making it a vasopeptidase inhibitor.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because Aliskiren's mechanism is accurately described as inhibiting renin, not its secretion.
**Option B:** Incorrect as it inaccurately describes Losartan's mechanism of action.
**Option C:** Incorrect because while Enalapril can cause cough and angioedema, the description of Losartan is incorrect.
**Option D:** Incorrect as Eplerenone is less likely to cause gynaecomastia, and the description of Sampatrilat is correct but does not make the entire statement true.

**Clinical Pearl / High-Yield Fact**
Remember, **ACE inhibitors** like Enalapril can cause a dry cough and angioedema due to increased **bradykinin** levels. **Direct renin inhibitors** like Aliskiren offer an alternative approach to RAAS blockade.

**Correct Answer: D.**

✓ Correct Answer: C. True: 2, 5; False: 1, 3, 4