Daptomycin versus Vancomycin for Empiric Treatment of Methicillin-Resistant S. aureus among Hospitalized Patients: An Institutional Cost-Breakpoint Analysis
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Background: Bacteremia caused by methicillin-resistant Staphylococcus aureus is associated with increased hospitalization days, costs, and mortality. Daptomycin was shown to be noninferior to vancomycin in a phase III clinical trial; however the study was limited by low rates of MRSA infection and before the emergence of strains with reduced susceptibility to vancomycin. Purpose: The purpose of this study was to perform a cost-breakpoint analysis comparing daptomycin versus vancomycin as empiric therapy for methicillin-resistant Staphylococcus aureus bacteremia. Methods: Data from a phase III, randomized clinical trial comparing daptomycin to vancomycin was used to build a cost breakpoint model. Costs and clinical outcomes associated with drug purchase, toxicity management, vancomycin-resistance, and likelihood of empiric therapy correctly given to patients with confirmed S. aureus bacteremia were added to the model. The model was then used to assess when daptomycin may be beneficial for empiric treatment. Results: The decision model was able to mimic the results of the phase III clinical trial. Holding other parameters constant, the results showed that empiric treatment correctly directed to S. aureus bacteremia of at least 40% (assumed MIC: 0.5 mcg/ml), a MIC of 1.0 – 1.5 mcg/ml (correct empiric therapy: 30%), or a MIC of 2.0 (correct empiric therapy: 20%), daptomycin was more cost-effective than vancomycin as empiric MRSA bacteremia treatment. Conclusion: With increasing vancomycin MRSA MIC against S. aureus, daptomycin may be an appropriate choice of empiric therapy for suspected bacteremia is certain cases.