title: Dose-dependent pharmacokinetics of a new oral cephalosporin, cefixime, in the dog.
abstract: Cefixime (CL 284,635; FK 027) is a new third-generation oral cephalosporin. To study dose-dependent pharmacokinetics of cefixime in dogs, two balanced four-way crossover studies were conducted. In the first study, oral doses of 50, 100, and 200 mg/kg and an intravenous dose of 50 mg/kg cefixime were administered. In the second study, oral doses of 6.25, 12.5, and 25 mg/kg and an intravenous dose of 12.5 mg/kg cefixime were administered to the same dogs. A period of 1 month separated the two studies. When the two intravenous doses were compared (i.e., 12.5 and 50 mg/kg), a twofold increase in clearance and volume of distribution was observed after the higher dose. The oral systemic bioavailability in the dose range 6.25-50 mg/kg was 55%. It decreased to 44% at 100 mg/kg and 27% at 200 mg/kg. The average peak serum concentrations ranged from 15.8 micrograms/ml at 6.25 mg/kg to 119 micrograms/ml at 200 mg/kg. Within this concentration range, the fraction of free drug in serum (unbound to proteins) increased from 7 to 25%. This concentration-dependent protein binding was primarily responsible for changes in total clearance, volume of distribution, and bioavailability of the drug in dogs.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D020682:Cefixime; D002439:Cefotaxime / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D007275:Injections, Intravenous
chemical_list: D020682:Cefixime; D002439:Cefotaxime