Initial trough concentration may be beneficial in preventing linezolid-induced thrombocytopenia.

We assessed whether prospective therapeutic drug monitoring to optimise the therapeutic range could prevent linezolid-induced thrombocytopenia. This prospective interventional study was conducted from September 2017 to October 2020 among 37 adult patients receiving linezolid. Patients were administered one of the following two initial dosages: 600 mg twice or once daily for patients with a creatinine clearance rate of ≥50 or <50 mL/min, respectively. Linezolid dosage adjustment was performed on days 3-5 based on the trough concentration. The serum linezolid levels in 22 and 15 patients were within and above the therapeutic range (2-7 µg/mL), respectively. The incidence of thrombocytopenia was significantly lower among patients whose linezolid levels were within the therapeutic range (4.5%;1/22) than in those whose levels were above the therapeutic range (80%; 12/15). It is important to maintain the linezolid level within the therapeutic range at the first therapeutic drug monitoring to prevent thrombocytopenia.