LInezolid Monitoring to MInimise Toxicity (LIMMIT1): A multicentre retrospective review of patients receiving linezolid therapy and the impact of therapeutic drug monitoring

Background: Linezolid is a broad-spectrum antimicrobial with limited use due to toxicity. This study aimed to evaluate linezolid toxicity in a large multicentre cohort. Secondary objectives were to identify factors contributing to toxicity, including the impact of therapeutic drug monitoring (TDM).

Methods: Patients administered linezolid between January 2017 and December 2019 were retrospectively reviewed. Data were collected on patient characteristics, linezolid therapy and outcomes. Descriptive statistics were performed on all patients, and statistical comparisons were undertaken between those who did and did not experience linezolid toxicity. A multivariable logistic regression model was constructed to identify any covariates that correlated with toxicity.

Results: Linezolid was administered to 1050 patients; of these, 381 did not meet the inclusion criteria and 47 were excluded as therapy ceased for non-toxicity reasons. There were 105 of 622 (16.9%) patients assessed to have linezolid toxicity. Patients who experienced toxicity displayed a higher baseline creatinine (96.5 μmol/L vs. 79 μmol/L; P = 0.025), lower baseline platelet count (225 × 10⁹/L vs. 278.5 × 10⁹/L; P = 0.002) and received a longer course (median 21 vs. 14 days; P < 0.001) than those who did not. Linezolid TDM was performed in 144 patients (23%). Multivariable logistic regression demonstrated that TDM-guided appropriate dose adjustment significantly reduced the odds of linezolid toxicity (aOR = 0.45; 95% CI 0.21–0.96; P = 0.038) and a treatment duration > 28 days was no longer significantly associated with toxicity.

Conclusions: This study confirmed that linezolid treatment-limiting toxicity remains a problem and suggests that TDM-guided dose optimisation may reduce the risk of toxicity and facilitate prolonged courses beyond 28 days.