A patient on an MDR-TB regimen containing linezolid develops progressive numbness and paraesthesia in both feet after 3 months. Peripheral blood smear shows macrocytic anaemia. Which mechanism explains both findings?
- A Linezolid inhibits mitochondrial protein synthesis by binding to mitochondrial ribosomes ✓
- B Linezolid inhibits mycobacterial DNA gyrase, causing mitochondrial toxicity
- C Linezolid chelates pyridoxine, causing functional B6 deficiency
- D Linezolid inhibits dihydropteroate synthase in human cells
Correct answer: A. Linezolid inhibits mitochondrial protein synthesis by binding to mitochondrial ribosomes
Explanation
Linezolid binds the 23S rRNA of the 50S ribosomal subunit, inhibiting protein synthesis in both bacteria and human mitochondria. Prolonged use (>28 days) causes mitochondrial toxicity manifesting as peripheral neuropathy, optic neuropathy, and myelosuppression (including sideroblastic/macrocytic anaemia). Dose reduction to 300 mg/day or intermittent dosing (600 mg thrice weekly) is recommended in prolonged MDR-TB regimens.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.