The penetration of novel intravenous cephalosporins into the lung.

Relating the concentrations of active antimicrobial at the potential site of infection to MIC, may give some indication of clinical efficacy. Where relatively insusceptible pathogens are involved, site concentrations are likely to be important predictors of efficacy. Unfortunately, there are sources of errors in measurement which make the values obtained imprecise. Despite this, broad trends are beginning to emerge, especially with bronchial biopsy concentrations. In bronchial biopsies, cephalosporins reach approximately 35 to 55% of simultaneous serum concentrations, in whole lung tissue 15 to 50% and in ELF 15 to 35%. The observed site to serum ratios are consistent with the permeability characteristics of cephalosporins and the barriers to movement of drugs into sites of infection. There is evidence that inflammation may alter the barriers to infection and for the cephalosporins site penetration may be higher. Further work is necessary to establish a clear relationship between site concentrations in the lung and clinical efficacy.