ACEi / ARB
Formal Definition
ACE inhibitors (e.g., lisinopril, enalapril) block angiotensin-converting enzyme to reduce angiotensin II production; ARBs (e.g., losartan, valsartan) block angiotensin II at the AT1 receptor directly; both reduce afterload, decrease proteinuria, and are first-line in heart failure with reduced ejection fraction, hypertension, and diabetic nephropathy.
How It's Used on the Ward
"On an ACE" or "switched to an ARB" — ubiquitous on medicine floors; frequently held during AKI or hypotension.
Example
""Hold the lisinopril — Cr jumped from 1.1 to 2.3 after starting it two weeks ago. That's an ACEi-related Cr bump. Holding now: if Cr normalizes in 48 hours, that's probably bilateral renal artery stenosis. Renal ultrasound ordered.""
Clinical Context
ACEi/ARB cause a predictable 10–15% rise in Cr from efferent arteriole dilation — acceptable and expected. A >30% rise suggests renal artery stenosis or severe volume depletion. Main ACEi side effect: dry cough (bradykinin-mediated, 5–20% of patients) — switch to ARB. Angioedema (rare, serious) is a class effect of ACEi; if prior angioedema on ACEi, do NOT use ARB (different mechanism but ~10% cross-reactivity reported). Never combine ACEi + ARB (dual RAAS blockade increases AKI/hyperkalemia without added benefit).