Pharmacokinetics of ceftiofur sodium in equine pregnancy.

The study examines the absorption, distribution, metabolism, and excretion of the antimicrobial drug ceftiofur sodium in pregnant horses. It finds that the drug doesn’t appear to significantly cross the fetal membranes, thus potentially limiting its antimicrobial efficacy in the fetus.

Study Design

• The researchers worked with eleven pregnant pony mares, who were given ceftiofur sodium once a day, via intramuscular injections.
• They were given one of two doses—either 2.2mg/kg or 4.4mg/kg.
• The researchers collected plasma samples at several time points both before and after administering the antibiotic.
• Eight mares were brought back into the study close to their expected foaling —the childbirth process in horses— dates.
• These mares were also given daily doses of ceftiofur sodium to ensure steady concentrations of the drug at foaling time.
• Parturition (childbirth) was induced in the mares using oxytocin, another hormone, one hour after antibiotic administration.
• The researchers then collected a variety of samples, including allantoic and amniotic fluid, colostrum (the mare’s first milk), and placental tissues, as well as plasma samples from the foals themselves.

Results and Interpretation

• The team used high-performance liquid chromatography to measure the concentration of desfuroylceftiofur acetamide (DCA), the active form of ceftiofur sodium, in their collected samples.
• They noted that peak serum concentrations of DCA after administration were directly proportional to the dose—higher doses led to higher concentrations.
• Additionally, the drug was metabolized and eliminated quicker after administration of the lower dose compared to the higher dose.
• At the time of foaling, the researchers observed a mean serum DCA concentration within the mares, and also detected a mean concentration in the colostrum.
• However, DCA concentrations in allantoic and amniotic fluid, placental tissues, and the foals’ plasma were consistently below the limit of quantification, suggesting that the drug was not being efficiently transferred across the fetal membranes.

Conclusion

• The results of the study suggest that the administration of ceftiofur sodium may not effectively safeguard foals, as the drug appears to have difficulty crossing the fetal membranes.
• This implies a potential limitation in achieving antimicrobial efficacy against pathogens in the fetus when administering ceftiofur sodium to pregnant mares.