Pharmacokinetics of moxalactam and cefazolin compared in normal volunteers

The pharmacokinetics of moxalactam, a new beta-lactam antibiotic with an unusually broad spectrum of activity, were studied in normal volunteers and compared with the pharmacokinetics of cefazolin. After a 1,000-mg intramuscular injection of moxalactam, a mean peak serum level of 49 +/- 10 micrograms/ml was achieved at 30 to 60 min which was equivalent to the level achieved with 0.5 g of cefazolin. Serum levels of 4.57 +/- 0.63 micrograms/ml, above the inhibitory levels for most organisms, were present at 8 h. The half-life of moxalactam was 2.3 h. After a 30-min intravenous infusion of 1 g, the serum level of moxalactam was 60 +/- 18.8 micrograms/ml. This compares with a serum level of 70 micrograms/ml obtained with an infusion of 0.5 g of cefazolin. At 6 h, 3.59 +/- 0.68 microgram/ml of moxalactam was present. The half-life of moxalactam was 2.3 h, similar to that of cefazolin. By 1 h after administration, serum levels of moxalactam were higher after intramuscular administration than after intravenous delivery. Urinary recovery of the drug was 76% after intramuscular injection and 74% after intravenous infusion, with the majority of the drug having been excreted in the first 4 h after administration. Urinary recovery of cefazolin was 85%. The pharmacokinetics of moxalactam are similar to those of cefazolin.