A 52-year-old man with essential hypertension and type 2 diabetes mellitus presents for antihypertensive therapy. He has mild proteinuria and a serum creatinine of 1.2 mg/dL. Which drug is the preferred first-line agent for this patient?

Explanation

## Rationale for ACE Inhibitor as First-Line **Key Point:** ACE inhibitors are the preferred first-line antihypertensive in diabetic patients with evidence of renal involvement (proteinuria, elevated creatinine). ### Mechanism of Renoprotection 1. Dilate efferent arterioles of the glomerulus → reduce intraglomerular pressure 2. Reduce proteinuria independent of blood pressure lowering 3. Slow progression of diabetic nephropathy 4. Decrease aldosterone-mediated fibrosis **High-Yield:** ACE inhibitors and ARBs are the ONLY antihypertensives with proven renoprotective effects in diabetic patients. They reduce proteinuria and slow GFR decline. ### Comparison with Other Options | Agent | Mechanism | Renal Effect | Use in DM + Proteinuria | |-------|-----------|--------------|------------------------| | ACE inhibitor (Lisinopril) | Blocks angiotensin II formation | Renoprotective | **First-line** | | ARB | Blocks AT1 receptor | Renoprotective | Alternative if ACE-I intolerant | | Calcium channel blocker | Vasodilation | Neutral/reflex tachycardia | Second-line | | Thiazide diuretic | Inhibits Na-Cl cotransporter | Worsens glucose control | Avoid in DM | | Beta-blocker | β1 antagonism | Neutral/mask hypoglycemia | Not preferred | **Clinical Pearl:** The presence of proteinuria in a diabetic patient is a **red flag** for progressive nephropathy. ACE inhibitors are indicated regardless of blood pressure level in this scenario. **Mnemonic:** **RAAS** = Renin-Angiotensin-Aldosterone System — ACE inhibitors block this system, providing dual benefit: BP reduction + renal protection. [cite:KD Tripathi 8e Ch 31]