Patterns of Care and Treatment Outcomes for Outpatient Daptomycin-Containing Regimens in Osteomyelitis.

BACKGROUND: Use of daptomycin at doses ≥ 6 mg/kg for treatment of osteomyelitis is increasing in clinical practice; unfortunately, limited data are available to guide optimal dosing and duration. The objective of this study was to assess daptomycin dosing and duration regimens for osteomyelitis treatment. METHODS: This was a retrospective, multi-site, cohort study conducted in an integrated healthcare delivery system. Nonpregnant patients ≥ 18 years of age with osteomyelitis diagnosed between November 1, 2003 and June 30, 2011, ≥ 2 weeks outpatient daptomycin therapy, and ≥ 1 month of follow-up were included. Daptomycin doses < 6 mg/kg and ≥ 6 mg/kg at durations of < 6 weeks and ≥ 6 weeks were examined with univariate and multivariate analyses to assess treatment success and all-cause mortality. RESULTS: A total of 247 patients were included, with 39 (15.8%), 37 (15.0%), 107 (43.3%), and 64 (25.9%) receiving < 6 mg/kg and ≥ 6 weeks, < 6 mg/kg and < 6 weeks, ≥ 6 mg/kg and ≥ 6 weeks, and ≥ 6 mg/kg and < 6 weeks of daptomycin therapy, respectively. Patients had a mean age of 58 years and had received prior vancomycin therapy (65.6%). Patients receiving < 6 weeks of therapy were less likely to experience treatment success compared with ≥ 6 weeks (41.5% vs 25.3%, adjusted odds ratio = 0.55; 95% confidence interval = 0.31-0.98) independent of duration. There were no differences across groups in mortality after adjustment. CONCLUSION: In a diverse clinical population, daptomycin for treatment of osteomyelitis of 6 weeks or longer duration was associated with success independent of dose. This finding supports longer treatment with daptomycin as a first-line agent in antimicrobial stewardship initiatives.