In acute renal failure, which drug requires dosage adjustment?

• A. Gentamicin sulfate
• B. Acetaminophen
• C. Furosemide
• D. Penicillin G

Answer: (A)

In acute kidney injury, drugs that are cleared by the kidneys must be adjusted to prevent accumulation and toxicity because the kidneys aren’t filtering as well. Gentamicin is an aminoglycoside with a very narrow therapeutic index and is almost exclusively excreted by the kidneys. When kidney function is impaired, trough levels can rise quickly, leading to nephrotoxicity and ototoxicity. To avoid this, the dose is reduced or the dosing interval is lengthened, and trough levels are monitored to keep drug exposure within a safe range.

Acetaminophen is mainly processed by the liver, so renal failure doesn’t typically necessitate major dose changes for this drug. Penicillin G and furosemide do require caution and often renal-dose adjustments, but the clear and most critical example in this scenario is the aminoglycoside due to its direct nephrotoxicity risk and reliance on renal clearance.