In vivo, daptomycin administered at 10 mg/kg twice daily significantly reduces bacterial load in the kidneys of infected models within 48 hours of starting treatment. When the dose is increased to 20 mg/kg and administered once daily, it becomes less effective initially but still significantly reduces bacterial colonies after four days of treatment. The efficacy of this regimen is comparable to that of vancomycin or combined vancomycin-gentamicin therapy administered twice daily^[2].

Daptomycin exhibits strong in vitro inhibitory and bactericidal activity against a range of bacterial strains. It is notably effective against nafcillin-susceptible and resistant staphylococci with a MIC90 (minimum inhibitory concentration for 90% of organisms) of ≤0.5 mg/L, and against enterococci with a MIC90 of ≤2.0 mg/L. Daptomycin demonstrates greater efficacy than vancomycin against most isolates tested. It stands out as the most potent agent against nafcillin-resistant staphylococci and ranks among the most effective treatments for enterococci, excluding trimethoprim-sulfamethoxazole. Notably, both daptomycin and vancomycin exhibit an increase in MIC when the bacterial inoculum is increased from 10⁵ to 10⁷ nM cfu/mL, suggesting a dose-dependent response to larger bacterial populations^[1].

Daptomycin's efficacy is contained within a relatively narrow concentration range, from 0.125 to 2.0 mg/mL, showing higher activity compared to other agents tested against S. faecalis ^[2].

Additionally, daptomycin has been found to inhibit the formation of nucleotide-linked intermediates in bacterial biosynthetic processes^[3].