A patient with XDR-TB who has received linezolid 600 mg daily for five months develops burning pain and numbness in both feet along with declining visual acuity. Which underlying mechanism best explains this combination?
- A Mitochondrial protein synthesis inhibition causing dose- and duration-dependent peripheral and optic neuropathy ✓
- B Inhibition of bacterial RNA polymerase with cross-reactive neural injury
- C Accumulation of the drug in lens tissue causing refractive change
- D Autoimmune demyelination triggered by the drug
Correct answer: A. Mitochondrial protein synthesis inhibition causing dose- and duration-dependent peripheral and optic neuropathy
Explanation
Linezolid binds the 23S ribosomal RNA of the 50S subunit and, importantly for prolonged anti-TB use, also inhibits mitochondrial ribosomal protein synthesis. Toxicity is time- and exposure-dependent: myelosuppression, lactic acidosis, painful peripheral neuropathy and optic neuritis. Neuropathy may be irreversible, so visual and neurological monitoring and dose reduction are essential during extended linezolid courses for drug-resistant TB.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.