Which anti-TB drug is an aminoglycoside with a risk of ototoxicity and nephrotoxicity?

• A. Streptomycin
• B. Ethambutol
• C. Isoniazid
• D. Rifampin

Answer: (A)

Streptomycin is an aminoglycoside used in TB treatment, and it directly fits the toxicity pattern described. Aminoglycosides work by binding the 30S subunit of bacterial ribosomes, causing misreading of mRNA and inhibition of protein synthesis, which makes them bactericidal. Among the TB drugs listed, only streptomycin belongs to the aminoglycoside class. A hallmark toxicity of aminoglycosides is ototoxicity, which can affect hearing and balance, and nephrotoxicity, with potential rises in creatinine and impaired kidney function. These risks are especially important in patients with renal impairment or when trough levels are high or other nephrotoxic drugs are used. The other drugs have different toxicity profiles: ethambutol mainly causes optic neuropathy; isoniazid causes hepatotoxicity and peripheral neuropathy; rifampin causes hepatotoxicity and strong drug interactions. So the drug that is an aminoglycoside with a risk of both ototoxicity and nephrotoxicity is streptomycin.