ONCE-A-DAY CEPHALOSPORINS - REALITY OR MYTH

The factors that may influence the pharmacodynamics of antimicrobial a gents against microorganisms at the site of infection must be consider ed before using once-daily antimicrobial chemotherapy in clinical prac tice. From a pharmacokinetic point of view, we can establish which ant ibiotic is suitable for once-daily therapy. For aminoglycosides and qu inolones, where the bacterial killing is rapid and dose dependent, and there is a post-antibiotic effect (PAE), the pharmacodynamic objectiv e is to maintain the tissue levels way above the minimum inhibitory co ncentration (MIG) for a short period. This can be achieved by giving s ingle bolus doses at long time intervals. With beta-lactam antibiotics , however, which have a slow time-dependent antibacterial effect and d o not display a PAE, the aim is to keep the antibiotic concentration a bove the MIC for the duration of therapy.