Daptomycin and Quinupristin-Dalfopristin

DAPTOMYCIN •Daptomycin is a cyclic lipopeptide that targets the cell membrane of gram-positive bacteria in a calcium-dependent manner. •The antimicrobial activity closely overlaps that of glycopeptides, and the drug retains some activity against most organisms with decreased susceptibility to glycopeptides. •It is approved for treatment of acute bacterial skin and skin structure infection (ABSSSI) caused by gram-positive cocci and for Staphylococcus aureus bacteremia, including right-sided endocarditis. •Administered intravenously, once daily; the approved doses are 4 and 6 mg/kg/day for ABSSSI and for S. aureus bacteremia and right-sided endocarditis, respectively. Some experts recommend higher doses (8 to 12 mg/kg/day) for serious infections. Dosage adjustment is required if the creatinine clearance is less than 30 mL/min. •Reversible muscle toxicity is the main adverse event. Less frequent adverse events are paresthesias, peripheral neuropathies, and eosinophilic pneumonia. •Combinations of daptomycin and β-lactams are potential options for recalcitrant infections. QUINUPRISTIN-DALFOPRISTIN •Quinupristin-dalfopristin contains a streptogramin B (quinupristin) and a streptogramin A (dalfopristin) component in a 30 : 70 ratio. •Quinupristin-dalfopristin is active against most gram-positive organisms (except Enterococcus faecalis) and a few gram-negative organisms. •Variable rates of resistance among Enterococcus faecium isolates have been reported. •The dosage is 7.5 mg/kg every 12 hours for ABSSSI caused by S. aureus and Streptococcus pyogenes. Dosage adjustment is not required in renal failure, but a lower dose may be considered with hepatic disease. •Irritation at the venous site is common when the drug is administered through peripheral veins. Arthralgias and myalgias may lead to drug discontinuation. •US Food and Drug Administration approval for use with vancomycin-resistant enterococci (VRE) was withdrawn after the initial trials failed to prove clinical benefit.