Vancomycin: a 50-something-year-old antibiotic we still don't understand.

Because a significant proportion of Staphylococcus aureus strains as well as most coagulase-negative staphylococci are resistant to penicillin and semisynthetic beta-lactam drugs, the need for vancomycin and related antibiotics has never been greater. Effective use of vancomycin requires knowledge of dosing parameters and selection of target trough levels appropriate to the specific infection and to the pathogen being treated. For clinicians, it is vital to remain up-to-date with evolving definitions for vancomycin susceptibility, with new interpretations of efficacy, and with information on toxicity.