Studies on protein binding of antibiotics. III. Effect of novobiocin on protein binding and pharmacokinetics of cefoperazone and cefazolin.

The drug-protein interactions between cefoperazone (CPZ) and apalcillin (APPC), and between cefazolin (CEZ) and APPC were investigated in in vitro and in vivo experiments. Though the binding rates of CPZ or CEZ to rabbit serum and human serum albumin subsided remarkably with increased drug concentrations, APPC was not greatly affected, even at high concentrations. It appeared that APPC had a higher binding capacity to protein than CPZ or CEZ. From the results of competitive study, it became clear that APPC partially shared the binding sites on protein with CPZ or CEZ. The CPZ or CEZ serum levels in rabbits administered together with APPC were not different from those for the single administration, but APPC levels for the simultaneous administration were slightly lower.