Disposition of firocoxib in late pregnant and early postpartum mares.

This research article investigates the effect of pregnancy on the way in which a drug called firocoxib is processed by the body, focusing specifically on late pregnant and newly postpartum mares. The study found that pregnancy did affect drug processing, with lower plasma concentrations of firocoxib observed in pregnant mares as compared to those that had just given birth.

Objectives and Study Design

• The primary goal of this study was to explore how pregnancy might influence the “disposition” – meaning the absorption, distribution, metabolism, and excretion – of a drug known as firocoxib when it’s administered to a mare orally.
• For this investigation, the researchers chose seven pony mares. These animals were given an oral paste containing 0.1 mg/kg of firocoxib, first during the later stages of pregnancy and then again 12 to 33 days after giving birth.

Methods of Analysis

• The researchers used high-performance liquid chromatography (HPLC) combined with ultraviolet detection to measure the concentration of firocoxib in the mares’ plasma. This method allowed them to characterize the drug’s disposition.

Key Findings

• The results indicated that maximum plasma concentrations of firocoxib were significantly lower in pregnant mares (averaging 50.0 ± 21.8 ng/mL) compared to postpartum mares (averaging 73.7 ± 25.6 ng/mL). This difference signifies that pregnancy does affect how firocoxib is processed in the body.
• However, the plasma concentrations of the drug 24 hours after administration, the time it took to reach maximum plasma concentrations, and the area under the plasma concentration versus time curve, were not significantly different for late stage pregnancy and postpartum periods. These findings suggest that while the highest concentration of the drug that gets into the blood (max plasma concentration) is affected by pregnancy, the overall process of drug absorption and elimination remains the same during late pregnancy and early postpartum.