What is a major safety concern with polymyxins such as colistin?

• A. Hepatotoxicity
• B. Ototoxicity
• C. Nephrotoxicity and neurotoxicity
• D. Anemia

Answer: (C)

Polymyxins carry significant toxicity to the kidneys and the nervous system, and these are the major safety concerns with drugs like colistin. Nephrotoxicity is the most common and often dose-limiting, showing up as rising serum creatinine and reduced glomerular filtration rate. The risk rises with higher doses, preexisting kidney disease, dehydration, older age, and concurrent nephrotoxic medications, so careful dosing and monitoring of renal function are essential.

Neurotoxicity can occur as well, presenting with symptoms such as dizziness, paresthesias, neuromuscular weakness, and, in severe cases, respiratory compromise due to neuromuscular blockade. This risk increases with higher systemic exposure and impaired clearance.

Hepatotoxicity and anemia are not typical primary concerns with polymyxins, and while ototoxicity can be reported, it is less common than nephro- and neurotoxicity. Hence, the major safety concerns are nephrotoxicity and neurotoxicity.