Disposition of orally administered cefpodoxime proxetil in foals and adult horses and minimum inhibitory concentration of the drug against common bacterial pathogens of horses

Abstract

To determine the disposition of orally administered cefpodoxime proxetil in foals and adult horses and measure the minimum inhibitory concentrations (MICs) of the drug against common bacterial pathogens of horses. 6 healthy adult horses and 6 healthy foals at 7 to 14 days of age and again at 3 to 4 months of age. A single dose of cefpodoxime proxetil oral suspension was administered (10 mg/kg) to each horse by use of a nasogastric tube. In 7- to 14-day-old foals, 5 additional doses were administered intragastrically at 12-hour intervals. The MIC of cefpodoxime for each of 173 bacterial isolates was determined by use of a commercially available test. In 7- to 14-day-old foals, mean +/- SD time to peak serum concentration (Tmax) was 1.7 +/- 0.7 hours, maximum serum concentration (Cmax) was 0.81 +/- 0.22 microg/mL, and elimination half-life (harmonic mean) was 7.2 hours. Disposition of cefpodoxime in 3- to 4-month-old foals was not significantly different from that of neonates. Adult horses had significantly higher Cmax and significantly lower Tmax, compared with values for foals. The MIC of cefpodoxime required to inhibit growth of 90% of isolates for Salmonella enterica, Escherichia coli, Pasteurella spp, Klebsiella spp, and beta-hemolytic streptococci was 0.38, 1.00, 0.16, 0.19, and 0.09 microg/mL, respectively. Oral administration at a dosage of 10 mg/kg every 6 to 12 hours would appear appropriate for the treatment of equine neonates with bacterial infections.