Identify two common nephrotoxic medications to avoid or use with caution in reduced kidney function.

• A. ACE inhibitors and ARBs
• B. Statins and metformin
• C. Beta-blockers and calcium channel blockers
• D. NSAIDs and aminoglycoside antibiotics

Answer: (D)

Recognizing medications that pose a risk to kidney function when renal function is reduced is essential. The two classic nephrotoxic medications to avoid or use with caution are NSAIDs and aminoglycoside antibiotics.

NSAIDs work by inhibiting prostaglandin synthesis. Prostaglandins help dilate the afferent arteriole and maintain adequate glomerular filtration, especially when kidney perfusion is already compromised (as in dehydration, CKD, or heart failure). Blocking these prostaglandins can lead to reduced renal blood flow and a drop in GFR, increasing the risk of acute kidney injury. Long-term use can also contribute to chronic kidney damage. If the kidneys aren’t clearing waste efficiently, it’s wise to avoid NSAIDs or use the smallest effective dose for the shortest duration, with careful hydration and monitoring, and consider safer alternatives like acetaminophen.

Aminoglycoside antibiotics (for example, gentamicin, tobramycin) are directly nephrotoxic because they accumulate in proximal tubular cells and cause cellular injury, leading to acute tubular necrosis. The risk is higher with higher drug levels, longer treatment, dehydration, or concomitant kidney impairment. When these drugs are necessary, dosing must be adjusted to kidney function, trough levels should be monitored, and renal function observed closely; alternatives with less nephrotoxicity should be used if possible.

Other options listed are less clearly nephrotoxic in typical scenarios, especially when kidney function is already reduced, and are often managed with appropriate monitoring and dosing adjustments.