Abstract
The pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin, as well as the placental transfer of enrofloxacin and ciprofloxacin, have not been studied. The aims of this study were (1) to evaluate the pharmacokinetics of enrofloxacin and ciprofloxacin by intravenous and intramuscular administration of 7.5 mg/kg in pregnant goats; (2) to determine the placental transfer of enrofloxacin and ciprofloxacin; (3) to conduct a PK/PD analysis to calculate the PK/PD cutoff of different dose regimens; and (4) to evaluate the tentative epidemiological cutoff values for coagulase-negative staphylococci wild-type isolates from goats. Plasmatic concentrations of enrofloxacin and ciprofloxacin in pregnant goats were well described by the parent-metabolite model. Simultaneous modeling of enrofloxacin and ciprofloxacin in each individual allowed for a PK/PD analysis that considered both drugs with antimicrobial activity. Our results show that both enrofloxacin and ciprofloxacin crossed the placenta in goats: fetal/maternal concentration ratio were 0.58 ± 0.05 and 0.03 ± 0.01 for enrofloxacin and ciprofloxacin. MIC values of coagulase-negative staphylococci isolates (n = 90) were obtained, and tentative epidemiological cutoffs were calculated at 0.25 and 0.5 mg/L for enrofloxacin and ciprofloxacin. According to PK/PDco values, an intravenous dose regimen of 10 mg/kg/day was considered the most appropriate, but based on the PK/PDco, culture, and AST data, an effective dosing regimen with the lowest possible dose could be selected to minimize the potential risk of fetal exposure to enrofloxacin.