Which adverse effects are major for linezolid in TB therapy?

• A. Bone marrow suppression, peripheral/optic neuropathy, and lactic acidosis with long-term use.
• B. Hypothyroidism
• C. Nephrotoxicity only
• D. Anaphylaxis

Answer: (A)

The main concept is that linezolid can cause mitochondrial toxicity, which leads to several serious adverse effects if used for prolonged periods as in TB therapy. Linezolid inhibits mitochondrial protein synthesis because mitochondrial ribosomes resemble bacterial ribosomes. This effect disrupts normal cell function, especially in cells that rely on high-energy processes.

Bone marrow suppression is a key risk, resulting in myelosuppression with decreases in red cells, white cells, and platelets. This can show up as anemia, increased infection risk, or bleeding tendencies and often becomes more likely during extended treatment. Peripheral neuropathy and optic neuropathy are also major concerns; patients may notice numbness, tingling, or pain in the hands and feet, or changes in vision with longer courses. A less common but important consequence of long-term use is lactic acidosis, a serious metabolic disturbance caused by impaired mitochondrial function, which can present with fatigue, weakness, nausea, abdominal discomfort, and rapid breathing.

These toxicities are distinct from other potential adverse effects not typical of linezolid in TB, such as hypothyroidism, nephrotoxicity as a sole major issue, or rare reactions like anaphylaxis. Monitoring during therapy—regular blood counts and assessment for neuropathic symptoms and signs of lactic acidosis—is essential to catch these issues early.