Sacubitril/valsartan (LCZ696) is a first-in-class ARNI (angiotensin receptor-neprilysin inhibitor). Neprilysin inhibition reduces the degradation of natriuretic peptides. What is the clinical risk created by combining neprilysin inhibition with an ACE inhibitor (rather than an ARB)?

• A Hyperkalemia due to dual RAAS suppression
• B Life-threatening angioedema due to bradykinin accumulation from two independent pathways ✓
• C Severe hypotension due to natriuretic peptide-mediated excessive vasodilation
• D Rebound aldosteronism causing fluid retention

Explanation

ACE inhibitors prevent bradykinin degradation (normally catabolized by ACE/kininase II). Neprilysin also degrades bradykinin; therefore, combining sacubitril with an ACE inhibitor blocks two independent pathways of bradykinin catabolism, causing dangerous bradykinin accumulation with a markedly elevated risk of angioedema — a potentially life-threatening complication. This is why the combination is contraindicated, and sacubitril must always be paired with an ARB (valsartan in LCZ696). Hyperkalemia from dual RAAS blockade is a separate concern with ACEi + ARB combinations, not specifically angioedema.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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