Linezolid plasma concentrations and occurrence of drug-related haematological toxicity in patients with Gram-positive infections

Abstract Retrospective studies have documented a significant association between linezolid (LNZ) plasma concentrations and drug-related haematological toxicity. However, the safe upper threshold level for LNZ plasma trough concentrations ( C min values) has not been defined with certainty. A prospective observational study was performed aimed at comparing LNZ C min values in patients developing drug-related side effects with those measured in patients not experiencing LNZ toxicity. LNZ C min values were measured from the first week after starting therapy and were repeated periodically up to the end of treatment. Fifty patients, for a total of 210 LNZ C min evaluations, were considered. All patients ( n  = 9) who developed drug-related haematological toxicity also had significantly higher plasma LNZ C min values during the first week of therapy (9.0 ± 6.4 mg/L vs. 4.9 ± 3.7 mg/L; P P