indication

For the treatment of complicated skin and skin structure infections caused by susceptible strains of Gram-positive microorganisms.

pharmacology

Daptomycin is a 13 member amino acid cyclic lipopeptide antibiotic active against Gram-positive bacteria only. It has proven in vitro activity against enterococci (including glycopeptide-resistant Enterococci (GRE)), staphylococci (including methicillin-resistant Staphylococcus aureus), streptococci and corynebacteria. Daptomycin is derived from the fermentation product of Streptomyces roseosporus.

mechanism of action

Daptomycin appears to bind or insert into the outer membrane of gram positive bacteria. The binding and integration of daptomycin into the cell membrane is calcium dependent. Calcium ions cause a conformational change in daptomycin, augmenting its amphipathicity (hydrophilic head group and hydrophobic tail group), leading to incorporation into the cell membrane. This binding causes rapid depolarisation, resulting in a loss of membrane potential leading to inhibition of protein, DNA and RNA synthesis, which results in bacterial cell death. The bactericidal activity of daptomycin is concentration-dependent. There is in vitro evidence of synergy with β-lactam antibiotics.

biotransformation

Minor amounts of three oxidative metabolites and one unidentified compound have been detected in urine. The site of metabolism has not been identified.

half life

7 days

route of elimination

Daptomycin is excreted primarily by the kidney. In a mass balance study of 5 healthy subjects using radiolabeled daptomycin, approximately 78% of the administered dose was recovered from urine based on total radioactivity (approximately 52% of the dose based on microbiologically active concentrations) and 5.7% of the dose was recovered from feces (collected for up to 9 days) based on total radioactivity. Because renal excretion is the primary route of elimination, dosage adjustment is necessary in patients with severe renal insufficiency (CLCR <30 mL/min)