When initiating an ACE inhibitor, which monitoring is most essential to assess safety?

• A. Liver enzymes weekly
• B. Complete blood count daily
• C. Serum potassium and creatinine to assess risk of hyperkalemia and renal function
• D. Blood glucose weekly

Answer: (C)

Initiating an ACE inhibitor requires vigilant monitoring of renal function and potassium because these drugs can affect both. By blocking angiotensin II, ACE inhibitors reduce constriction of the efferent arteriole, lowering intraglomerular pressure and potentially decreasing the glomerular filtration rate. They also suppress aldosterone, which decreases potassium excretion in the distal nephron, increasing the risk of hyperkalemia. Because these effects can occur soon after starting therapy or after dose changes, the most essential safety checks are serum potassium and serum creatinine. Baseline values should be obtained, then rechecked within 1–2 weeks (and periodically thereafter, more often if risk factors are present). This approach directly targets the safety concerns with this drug class. Monitoring liver enzymes, CBC, or glucose is not specifically required to assess safety when starting an ACE inhibitor, as these are not the primary risks with ACE inhibitors.