Daptomycin

Daptomycin (5 μg/ml) reduces cell viability by >99% and membrane potential by >90% within 30 min in Staphylococcus aureus. Daptomycin exhibits rapid in vitro bactericidal activity against clinically significant strains of gram-positive pathogens including hemolytic streptococci, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci. Daptomycin acts at the cytoplasmic membrane of susceptible bacteria (8), as demonstrated by binding and fractionation studies. Daptomycin also differs from that of some antimicrobial peptides (e.g., human neutrophil peptide 1) that are capable of rapid depolarization of the cytoplasmic membrane but do not induce cell death for 1 hour to 2 hours. Daptomycin inserts into the cytoplasmic membrane of bacteria, as indicated by whole-cell and artificial membrane studies. ^[1] Daptomycin demonstrates greater bactericidal activity than all other drugs tested, killing ≥3 log CFU/ml by 8 hours. Daptomycin is a cyclic polypeptide derived from Streptomyces roseosporus and representing a class of antimicrobial agents known as the peptolides (acid lipopeptide antibiotics). Daptomycin is also active against vancomycin-resistant gram-positive bacteria, including enterococci. Daptomycin is highly protein bound (94%), and its in vitro activity is altered in the presence of serum or albumin.^[2] Daptomycin consists of a 13-member amino acid cyclic lipopeptide with a decanoyl side-chain, the lipophilic Daptomycin tail into the bacterial cell membrane, causing rapid membrane depolarization and a potassium ion efflux. Daptomycin treatment has been linked to fully reversible skeletal muscle toxicity with no effect on smooth or cardiac muscle. ^[3]

Daptomycin exhibited linear pharmacokinetics, with an area under the concentration-time curve (AUC) from time zero to infinity/dose of 9.4 and a half-life of 0.9 to 1.4 h. The level of protein binding was 90%^[5].