Which class of analgesics should be avoided when CrCl < 30 mL/min due to risk of AKI?

• A. Acetaminophen
• B. Codeine
• C. NSAIDs
• D. Tramadol

Answer: (C)

The key idea is that NSAIDs can trigger acute kidney injury in people with very reduced kidney function. In the kidneys, prostaglandins help dilate the afferent arteriole to keep glomerular filtration up when blood flow is low or volume is depleted. NSAIDs block prostaglandin synthesis, which can cause the afferent arteriole to constrict, lowering GFR and risking AKI. When the creatinine clearance is less than 30 mL/min, this risk is especially high, so NSAIDs should be avoided.

Acetaminophen typically doesn’t affect renal blood flow in the same way and is often safer for the kidneys at usual doses, though liver toxicity limits still apply. Codeine and tramadol are opioids whose main concerns in CKD are metabolite buildup and other systemic effects, not a direct, immediate risk of AKI from impaired renal perfusion.