Effects of Different Linezolid Concentration Levels on Hematologic Side Effects: A New Target for Therapeutic Drug Monitoring.

BACKGROUND

The emergence of a linezolid minimum inhibitory concentration creep (2-4 mg/L) necessitates higher trough concentrations (C min ), which may increase the risk of hematological side effects. Evaluating the effects of different linezolid C min levels on hematological indices and determining a new target C min range are essential.

METHODS

Elderly patients receiving linezolid at 4 tertiary hospitals between May 2021 and March 2024 were grouped according to their C min levels. Linezolid C min and hematological indices were monitored dynamically.

RESULTS

A total of 320 patients were enrolled, and 128 patients were included in the analysis of hematological side effects following propensity score matching between C min >16 mg/L and C min ≤16 mg/L. The incidence of thrombocytopenia and the reduction in platelet count were significantly greater in patients with C min >16 mg/L compared with those with C min ≤16 mg/L. However, no significant differences were observed in the incidence of anemia or changes in hemoglobin levels. Among the 96 patients with C min ≤16 mg/L, multivariate analysis identified C min as an independent risk factor for thrombocytopenia but not for anemia. Furthermore, no significant difference in thrombocytopenia risk was found between patients with C min levels of 8-14.5 mg/L and those with C min of <8 mg/L (odds ratio, 1.183; 95% confidence interval, 0.428-3.275; P = 0.746).

CONCLUSIONS

In elderly patients, hematological side effects did not increase with increasing C min levels up to 14.5 mg/L. These findings suggest that a target C min range of 2-14.5 mg/L may be appropriate for the elderly population receiving linezolid.

CLINICAL TRIAL REGISTRATION NUMBER: ChiCTR2100045707; April 23, 2021.