What is the role of linezolid in TB therapy and its major adverse effects?

• A. Used for MDR-TB/XDR-TB regimens; adverse effects include bone marrow suppression, peripheral/optic neuropathy, and lactic acidosis with long-term use.
• B. A first-line drug for drug-susceptible TB with minimal adverse effects.
• C. Inhibits mycolic acid synthesis.
• D. Increases energy production by stimulating ATP synthase.

Answer: (B)

Linezolid is used as a treatment option for MDR-TB and XDR-TB regimens, particularly when many first- and second-line drugs are ineffective or not tolerated. It is not a first-line drug for drug-susceptible TB because the standard regimen of isoniazid, rifampin, pyrazinamide, and ethambutol is preferred for initial cases due to proven efficacy and a more favorable safety profile. The major adverse effects to watch for are bone marrow suppression (which can lead to anemia or low platelets), peripheral neuropathy and optic neuropathy, and lactic acidosis with prolonged use. These toxicities are often related to cumulative exposure, so regular monitoring of blood counts, vision, and overall metabolic status is essential, and shorter or alternative regimens may be considered if toxicity arises. Linezolid can also interact with serotonergic medications, raising the risk of serotonin syndrome, so reviewing concurrent drugs is important. In short, its role is as a potent option for resistant TB with careful toxicity management, rather than a routine first-line choice.