Human serum protein binding of cephalosporin antibiotics in vitro.

The published values for serum protein binding of antibiotics vary considerably depending upon the method and experimental conditions used. A rapid, simple, and standardized ultrafiltration procedure for determination of the serum protein binding of antibiotics has been developed and used to compare the binding characteristics of four marketed cephalosporins. The human serum protein binding of cephradine, cephalexin, cephalothin, and cefazolin at 37 degrees C. and physiological pH (7.4) was found to be 13.8, 12.4, 71.2, and 89.2 per cent, respectively. These values fall within the range of published values for these antibiotics.