A 58-year-old woman starts linezolid for VRE bacteremia. She is counseled about a specific laboratory abnormality that must be monitored weekly if therapy continues beyond two weeks. The expected abnormality is:
- A Rising creatinine kinase indicating myopathy
- B Falling hemoglobin from pure red cell aplasia
- C Falling platelet count from time-dependent bone marrow suppression ✓
- D Rising transaminases indicating dose-dependent hepatotoxicity
Correct answer: C. Falling platelet count from time-dependent bone marrow suppression
Explanation
Linezolid causes reversible, time-dependent myelosuppression, with thrombocytopenia being the most common manifestation, typically appearing after about two weeks of continuous therapy. Weekly complete blood counts are recommended when treatment exceeds this duration. Myopathy and peripheral neuropathy are rare complications of very prolonged courses, and pure red cell aplasia is not the characteristic pattern. Hepatotoxicity is not a recognized major toxicity of linezolid. The mechanism involves interference with mitochondrial ribosomal protein synthesis.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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