Quinupristin-dalfopristin: a new antibiotic for severe gram-positive infections.

The steady increase in resistant organisms is related to the widespread use of antibiotics in community and hospital settings. New therapeutic options are needed, including treatments for infections caused by antibiotic-resistant gram-positive organisms. Quinupristin-dalfopristin, the first formulation of a distinct class of antibiotics known as the streptogramins, has activity against a range of gram-positive bacteria that are usually resistant to other agents, including vancomycin-resistant Enterococcus faecium. The pharmacodynamic (postantibiotic effect) and pharmacokinetic characteristics of quinupristin-dalfopristin allow dosing at eight- to 12-hour intervals. The safety profile of the formulation is generally favorable, with no demonstrable ototoxicity, nephrotoxicity, bone marrow suppression, or cardiovascular adverse effects. Reversible arthralgias, myalgias, and peripheral venous irritation are the formulation's major side effects. A potential for drug interactions exists because quinupristin-dalfopristin significantly inhibits the cytochrome P450-3A4 enzyme system. Quinupristin-dalfopristin has been shown to be effective in the management of documented severe infections caused by vancomycin-resistant E. faecium, nosocomial pneumonia, and infections related to the use of intravascular catheters.