What question did this study set out to answer?

To assess the impact of therapeutic drug monitoring on linezolid treatment outcomes and adverse effects in patients.

January 14, 2026Open Forum Infectious Diseases0 citationsOpen Access

P-1236. Clinical Impact of Linezolid Therapeutic Drug Monitoring

JJJoseph M. JohnsonVA Ann Arbor Healthcare System ESElizabeth Scruggs-WodkowskiUniversity of Michigan RWRobert WoodsUniversity of Michigan

Key Points

To assess the impact of therapeutic drug monitoring on linezolid treatment outcomes and adverse effects in patients.
Single-center retrospective cohort study
Involved patients anticipated to receive >14 days of linezolid therapy
Measured serum trough levels during treatment
Reviewed patient demographics and outcomes
Collected data on adverse effects, genomics, and dosing changes
30 encounters with 29 unique patients were examined
Only 31% of linezolid levels were within the therapeutic goal range
43% of patients required a dose decrease during treatment
50% experienced thrombocytopenia as an adverse effect
53% of patients avoided the use of PICCs

Abstract

Abstract Background Linezolid use is increasing in the outpatient setting to treat severe infections caused by Gram-positive bacteria, such as vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). Although FDA approved linezolid at a fixed dose of 600 mg twice daily, newer literature describes the importance of therapeutic drug monitoring (TDM) due to linezolid’s narrow therapeutic index and potential for adverse effects. We assessed the clinical impacts of a linezolid TDM process and possible associations between patient demographics and treatment outcomes at a Veterans Affairs Hospital.Figure 1.Platelet Count Over Time Methods This was a single-center retrospective cohort study of patients with anticipated 14-days of linezolid therapy and who had at least one serum trough level measured during their treatment course. Chart review occurred from January 2024 to December 2024. Data was collected on levels and changes to linezolid dosing, patient age, weight, renal function, WBC, platelet count, incidence of adverse effects, completion of intended duration of therapy, and peripherally inserted central catheter (PICC) avoidance. Results A total of 30 encounters including 29 unique patients were captured. Thirty-eight linezolid levels were collected (30 initial, 8 repeat) with a median value of 8.4 mcg/mL. Twelve levels (31%) resulted within the therapeutic goal range of 2-8 mcg/mL. Thirteen patients (43%) required a dose decrease prior to the end of treatment, and 14 patients (47%) discontinued linezolid due to adverse effects. The most common adverse effect was thrombocytopenia (15 patients, 50%). Only 4 patients (13%) completed their intended linezolid treatment course at the FDA approved dose of 600 mg twice daily with a therapeutic level and without the need for a dose reduction. PICCs were avoided in 16 patients (53%). Conclusion The majority of patients had linezolid trough levels above the therapeutic range when started on the standard FDA approved dose. TDM resulted in dose reductions and completion of the planned course in 13 of 30 patients, but thrombocytopenia was still common in the cohort. These findings suggest a need for additional studies to improve implementation of TDM and investigate alternative initial dosing in select patients. Disclosures All Authors: No reported disclosures

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