A 58-year-old man with hypertension and chronic kidney disease (eGFR 35 mL/min/1.73 m²) is evaluated for antihypertensive therapy. All of the following antihypertensives are considered renoprotective and appropriate first-line agents in CKD EXCEPT:

Explanation

## Renoprotective Antihypertensives in CKD ### Pathophysiology of CKD Progression **Key Point:** In chronic kidney disease, loss of nephrons triggers compensatory hyperfiltration in remaining glomeruli via: 1. Afferent arteriole dilation (increased glomerular hydrostatic pressure) 2. Efferent arteriole constriction (maintained by angiotensin II) This hyperfiltration accelerates proteinuria and further nephron loss. Renoprotective agents interrupt this cycle. ### Renoprotective Mechanisms (Options 0–2) **Option 0: ACE Inhibitors (e.g., Lisinopril)** **High-Yield:** ACE inhibitors preferentially dilate the **efferent arteriole** by blocking angiotensin II formation. This: - Reduces intraglomerular pressure (GFR may transiently ↓ 10–30%) - Decreases proteinuria - Slows CKD progression - First-line in CKD with albuminuria/proteinuria **Option 1: ARBs (e.g., Losartan)** **High-Yield:** ARBs selectively block AT~1~ receptors on the efferent arteriole, producing the same renoprotective effect as ACE inhibitors: - Reduce intraglomerular pressure - Decrease proteinuria - Equivalent to ACE inhibitors in slowing CKD progression - First-line alternative if ACE inhibitor intolerance (cough) **Option 2: Dihydropyridine CCBs (e.g., Amlodipine)** **Key Point:** Dihydropyridines dilate **both afferent AND efferent arterioles non-selectively**. This: - Reduces blood pressure effectively - Does NOT preferentially reduce intraglomerular pressure (unlike ACE-I/ARB) - May cause reflex tachycardia - Acceptable in CKD but NOT first-line for renoprotection - Used as add-on therapy or in patients intolerant to ACE-I/ARB ### NOT Renoprotective (Option 3: Spironolactone) **Warning:** Spironolactone is **NOT a first-line renoprotective agent** in CKD. Key concerns: 1. **Hyperkalemia risk:** Blocks aldosterone in collecting duct, reducing K^+^ excretion. In CKD (eGFR < 45), hyperkalemia risk is high and potentially life-threatening. 2. **No proven renoprotection:** Unlike ACE-I/ARB, spironolactone has NOT been shown to slow CKD progression as monotherapy. 3. **Contraindication in advanced CKD:** Generally avoided when eGFR < 30 mL/min/1.73 m² due to hyperkalemia risk. 4. **Limited role:** May be considered as an add-on agent in resistant hypertension with normal renal function, but NOT in this patient with eGFR 35. **Clinical Pearl:** The KDIGO 2021 guideline recommends ACE-I or ARB as first-line in CKD with albuminuria. Potassium-sparing diuretics are avoided in advanced CKD unless serum K^+^ is monitored closely and eGFR > 45. ### Comparison Table: Antihypertensives in CKD | Agent | Afferent Dilation | Efferent Dilation | Renoprotective | First-Line in CKD? | | --- | --- | --- | --- | --- | | ACE inhibitor | No | Yes | Yes | **Yes** | | ARB | No | Yes | Yes | **Yes** | | Dihydropyridine CCB | Yes | Yes | Partial | No (add-on) | | Non-dihydropyridine CCB | No | Yes | Partial | No | | Thiazide diuretic | — | — | No | No | | K^+^-sparing diuretic | — | — | No | **No (hyperkalemia)** | ```mermaid flowchart TD A[CKD with albuminuria/proteinuria]:::outcome --> B{First-line renoprotective agent?}:::decision B -->|ACE inhibitor| C[Lisinopril, enalapril, ramipril]:::action B -->|ARB| D[Losartan, valsartan, telmisartan]:::action B -->|Intolerant to ACE-I/ARB| E[Dihydropyridine CCB as add-on]:::action C --> F[Efferent arteriole dilation]:::outcome D --> F E --> G[Non-selective dilation<br/>Less renoprotection]:::outcome H[Spironolactone in CKD]:::urgent --> I[Hyperkalemia risk<br/>NOT first-line]:::urgent ``` [cite:KDIGO 2021 CKD Management Guidelines; Harrison 21e Ch 279]