In vitro antibacterial activity of cefoxitin and cefotetan and pharmacokinetics in dogs

Steven W. Petersen From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Eberhard Rosin From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Summary

The susceptibility of 50 clinical Escherichia coli isolates to various antibacterials, including cefoxitin and cefotetan was ascertained, and the minimal inhibitory concentration (mic) of cefoxitin and cefotetan for each of these isolates was determined. The pharmacokinetics of cefoxitin and cefotetan after a single iv or sc injection (30 mg/kg of body weight) were determined in 4 dogs. Of the 50 E coliisolates, 98% were susceptible in vitro to cefotetan, 90% were susceptible to cefoxitin, and 88% were susceptible to gentamicin. The mic that would inhibit the growth of 90% of the E coliisolates (mic90) was 0.25 µg/ml for cefotetan and 4 µg/ml for cefoxitin. Plasma cefotetan concentrations remained above mic90 for (mean ± SD) 8.2 ± 1.72 8.2 ± 1.72 hours and 13.52 ± 0.28 hours after iv and sc administration, respectively. Plasma cefoxitin concentrations remained above mic90 for (mean ± SD) 5.37 ± 1.18 hours and 7.95 ± 0.71 hours after iv and sc administration, respectively. We concluded that cefotetan was superior to cefoxitin·was superior to cefoxitin in activity against E coli in vitro. We recommend that cefotetan be given at a dosage of 30 mg/kg, iv, every 8 hours, Or sc, every 12 hours.

Summary

The susceptibility of 50 clinical Escherichia coli isolates to various antibacterials, including cefoxitin and cefotetan was ascertained, and the minimal inhibitory concentration (mic) of cefoxitin and cefotetan for each of these isolates was determined. The pharmacokinetics of cefoxitin and cefotetan after a single iv or sc injection (30 mg/kg of body weight) were determined in 4 dogs. Of the 50 E coliisolates, 98% were susceptible in vitro to cefotetan, 90% were susceptible to cefoxitin, and 88% were susceptible to gentamicin. The mic that would inhibit the growth of 90% of the E coliisolates (mic90) was 0.25 µg/ml for cefotetan and 4 µg/ml for cefoxitin. Plasma cefotetan concentrations remained above mic90 for (mean ± SD) 8.2 ± 1.72 8.2 ± 1.72 hours and 13.52 ± 0.28 hours after iv and sc administration, respectively. Plasma cefoxitin concentrations remained above mic90 for (mean ± SD) 5.37 ± 1.18 hours and 7.95 ± 0.71 hours after iv and sc administration, respectively. We concluded that cefotetan was superior to cefoxitin·was superior to cefoxitin in activity against E coli in vitro. We recommend that cefotetan be given at a dosage of 30 mg/kg, iv, every 8 hours, Or sc, every 12 hours.

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