SERUM-PROTEIN BINDING AND EXTRAVASCULAR DIFFUSION OF CEFODIZIME AND CEFTRIAXONE - AN IN-VIVO STUDY

The aim of the study was to investigate the concentration-time courses in serum and bronchial secretions of total and unbound cefodizime and ceftriaxone. These cephalosporins are similar in antibacterial spectr um, intrinsic activity and resistance to beta-lactamases, and differ i n serum protein binding and elimination half-life. 25 patients of eith er gender aged 48 to 68 years with acute exacerbation of chronic bronc hitis were treated every day with 1g intramuscularly of cefodizime or ceftriaxone. Free and total concentrations of the tested antibiotics w ere determined in duplicate by HPLC, both in serum and bronchial secre tion cleared from cells, at different times after the second dose. At 2, 4 and 6 hours, cefodizime was found to exhibit higher free concentr ations in bronchial secretion than those observed for ceftriaxone, des pite lower total blood and bronchial secretion concentrations. These d ata confirm that extravascular distribution of cephalosporins is influ enced by the extent of serum protein binding. Moreover, serum protein binding seems to affect the unbound concentration of cephalosporins at the site of infection.