Simulated Target Attainment of Multidose Regimens of Dalbavancin for Prolonged Durations of Therapy.

Background: Dalbavancin is a long-acting lipoglycopeptide antibiotic that is increasingly utilized for infections that require prolonged treatment durations despite the lack of Food and Drug Administration approval for these indications. There is no consensus regarding optimal dosing of dalbavancin for these infections and no available pharmacokinetic studies to identify optimal dosing for long-term use. Methods: An in silico pharmacokinetic simulation was performed to assess the predicted dalbavancin concentration resulting from commonly utilized dosing regimens, in addition to modified regimens. The primary endpoint evaluated was days of median 24-hour free area under the curve over the minimum inhibitory concentration (AUC/MIC) >27.1, the established PK target. Results: A dosing regimen of 1500 mg on day 0 and day 7 resulted in median AUC/breakpoint value above the target for 57 days (lower 95% confidence interval [CI], 37 days). A modified regimen of 1500 mg on day 0 and day 21 resulted in an additional 11 days of median AUC/breakpoint target attainment. The other standard dosing regimen modeled was 1000 mg on day 0, then 500 mg weekly for 5 doses. This regimen achieved the AUC/breakpoint target for 76 days (lower 95% CI, 59 days). This regimen was modified to 1000 mg on day 0, then 500 mg on days 14 and 28, which shortened the median effective treatment duration by 14 days but required 3 fewer doses. Conclusions: These simulated results, when combined with the favorable observational data, support the use of commonly reported dalbavancin regimens for prolonged therapy durations. In addition, these pharmacokinetic/pharmacodynamic data support extending the dosing interval beyond the frequently reported weekly regimens, which should be investigated further with a clinical trial.