4CPS-188 Therapeutic drug monitoring for dalbavancin suppressive therapy: optimising infusion spacing based on minimum inhibitory concentration

<h3>Background and Importance</h3> Dalbavancin is a long-acting antimicrobial used for suppressive therapy, with dosing adjusted through therapeutic drug monitoring (TDM) due to the lack of validated regimens. Recent expert recommendations propose a dosing schedule targeting a residual concentration above 8 mg/L, aimed at Staphylococcus species with a minimum inhibitory concentration (MIC) of 0.125 mg/L, the clinical breakpoint for dalbavancin. However, literature suggests that lower residual targets may be considered for MICs below 0.125 mg/L, potentially enabling longer administration intervals.¹ <h3>Aim and Objectives</h3> The aim is to demonstrate the benefits of using concentration thresholds adapted to the MIC of the bacteria for TDM and infusion spacing in patients treated with dalbavancin. <h3>Material and Methods</h3> This retrospective study (November 2017 to January 2024) included patients receiving dalbavancin as suppressive therapy. Dalbavancin levels were measured prior to each administration. Results were interpreted using either a target of 8 mg/L or a lower. According to the literature, the therapeutic target was adjusted proportionally: for instance, if the MIC was reduced by half, the target concentration was similarly reduced. This pattern continued as the MIC decreased further. <h3>Results</h3> Seven patients were included with a median age of 72 (63.5 – 79.5). Indications were mainly endovascular equipment infections (28,6%) and endocarditis (28,6%). Common pathogens included <i>Staphylococcus aureus</i> (28,6%), <i>Enterococcus faecalis</i> (28,6%) and coagulase-negative <i>Staphylococcus sp.</i> (14,3%). The median MIC was 0,047 mg/L (0.032–0.092 mg/L) and the median residual concentration was 6.95 mg/L (4.4–12 mg/L). Using a target of &gt;8 mg/L, 41% of dosing reached the goal, which increased to 90,6% when adjusted to the actual MIC, allowing injection spacing for these seven patients from 4 weeks at the beginning to 10 weeks in median (7–11). <h3>Conclusion and Relevance</h3> Adjusting dalbavancin dosing to the MIC improves therapeutic target achievement and enables longer dosing intervals, especially in suppressive therapy. However, clinical outcomes require further evaluation to validate these findings. <h3>References and/or Acknowledgements</h3> Cojutti PG, Rinaldi M, Gatti M, Tedeschi S, Viale P, Pea F. Usefulness of therapeutic drug monitoring in estimating the duration of dalbavancin optimal target attainment in staphylococcal osteoarticular infections: a proof-of-concept. <i>International Journal of Antimicrobial Agents</i>. 1 Nov 2021;<b>58</b>(5):106445. <h3>Conflict of Interest</h3> No conflict of interest