A 52-year-old man from Delhi presents with a 3-year history of hypertension. Current BP is 158/96 mmHg despite being on amlodipine 5 mg daily for the past 6 months. He has no history of diabetes, renal disease, or heart failure. Serum creatinine is 0.9 mg/dL, and urinalysis shows no proteinuria. His physician decides to add a second agent. Which of the following would be the most appropriate choice to add to amlodipine in this patient?

## Rationale for ACE Inhibitor Addition **Key Point:** When adding a second antihypertensive to a calcium channel blocker (CCB), an ACE inhibitor or ARB is the preferred choice due to complementary mechanisms and proven cardiovascular benefits. ### Why Lisinopril is Optimal 1. **Complementary mechanism**: Amlodipine causes peripheral vasodilation; lisinopril reduces angiotensin II-mediated vasoconstriction and aldosterone release. 2. **Synergistic BP reduction**: CCB + ACE inhibitor combinations are highly effective and well-tolerated. 3. **Cardiovascular protection**: ACE inhibitors reduce left ventricular hypertrophy, improve endothelial function, and reduce proteinuria (even without diabetes). 4. **No contraindications**: Normal renal function and no proteinuria make lisinopril safe. ### Evidence Base **High-Yield:** The 2017 ACC/AHA guidelines recommend ACE-I/ARB + CCB as a preferred dual-therapy combination for hypertension. This patient has no diabetes or CKD, so there is no additional renal protection urgency—but the synergy is still optimal. ### Mechanism of Synergy ```mermaid flowchart TD A[Amlodipine]:::action --> B[Peripheral vasodilation<br/>Reflex SNS activation]:::outcome C[Lisinopril]:::action --> D[Blocks Ang II<br/>Reduces aldosterone]:::outcome B --> E[Amlodipine-induced<br/>SNS activation]:::outcome D --> F[Lisinopril blunts<br/>SNS activation]:::outcome E --> G[Net: Additive BP reduction<br/>No tachycardia]:::outcome F --> G ``` **Clinical Pearl:** CCBs can cause reflex tachycardia and sympathetic activation; ACE inhibitors counteract this, making the combination synergistic rather than merely additive.