Monitoring antibiotic therapy in the newborn infant.

With antibiotic monitoring, antimicrobial therapy of the neonate can be safe and effective. During this period of transition, the pharmacokinetics of the infant is constantly in a state of flux. Treatment guidelines based on average pharmacokinetics do not always correspond to the values obtained from an individual infant. Individualization of therapy is the goal of monitoring antibiotic therapy in the newborn infant. The MIC and MBC data obtained from susceptibility testing are used to select the most appropriate antibiotic(s). The expected serum antimicrobial concentration should exceed the MIC and MBC by one to five times. Microbiologic, radioenzymatic, radioimmunoassay, high performance liquid chromatography, and other assay methods are currently available in the clinical laboratory. Adjustments of antimicrobial therapy are based on the information provided from assays of peak and trough serum concentration. Bactericidal titers indirectly provide similar information and are adequate for assessing therapy. Indications for monitoring antibiotic therapy in the newborn are dependent on the drug and clinical situation. Aminoglycoside and chloramphenicol, both of which have narrow ranges of serum concentration between efficacy and toxicity, require monitoring. Infants with serious or unusual infections benefit from assays of antibiotics. Other indications for monitoring antimicrobial concentrations are changes in methods of administration, multiple drug therapy, errors in medication, and any situation in which the information can be used to insure efficacy and safety.