Antimicrobial agents in rats. II. Serum levels of oral cephalosporins.

Cephalexin, cephradine and 7 beta-(D-2-amino-2-[(1,4-cyclohexadienyl)-acetamido])-3-methoxy-3-cephem-4-carboxylic acid (CGP 9000) were tested for their pharmacokinetic behaviour in rats. The cephalosporin serum concentrations were determined at certain times after oral administration of 150 mg/kg by the agar-well-diffusion method. The experiments revealed that the serum levels of cephalexin and cephradine did not differe essentially from one another. They maintained maximum serum concentrations of 30 microgram/ml to 40 microgram/ml during the first hour and than declined with a half-life of 2.5 h. CGP 9000 reached peak concentrations 60 to 90 min postdose and was eliminated with a half-life of 3.5 h. The area under the curve was double as large as those of cephalexin and cephradine. This may be a reason of favourable results in experimental chemotherapy with CGP 9000.