Antimicrobial agents in rats. I. Serum levels of parenteral cephalosporins.

Eleven cephalosporins were tested for their pharmacokinetic properties in rats in order to obtain a basis for experimental evaluation of their in vivo activity. The compounds were administered to female Wistar rats in i.m. doses of 150 or 50 mg/kg. The cephalosporin concentrations in rat serum were determined by the agar-well-diffusion method. Essential differences concerning the serum levels, half-life and the area under the curve could be ascertained. Low serum levels and short half-life could be reported for cephapirin, cephalotin, and cephradin, whereas cefazolin, cefazedone, and cefuroxime produced high and longer lasting serum levels. All cephalosporins were quickly absorbed, most of them were beneath the minimum detectable concentration after 6 h. It is concluded that pharmacokinetic data should be taken into consideration in conjunction with experimental chemotherapy.