Pharmacokinetics of single doses of maropitant citrate in adult horses.

The research investigates the pharmacokinetic profile, which includes distribution, absorption, and elimination, of single doses of maropitant citrate in adult horses. Maropitant citrate, typically used to alleviate nausea and vomiting in dogs and cats, was evaluated for use in horses through intravenous (IV) and intragastric (IG) administration schemes.

Study Design

• The study involved seven adult horses, making use of a randomized, crossover design. This method enables each horse to serve as its own control, contributing to a reduction in individual variability and the number of animals needed for the study.
• Single doses of maropitant citrate were administered intravenously at a concentration of 1mg/kg and intragastrically at 2mg/kg. These doses were decided based on maropitant’s usage in dogs and cats.
• For pharmacokinetic analysis, serial blood samples were taken from the horses following dosage administration. The maropitant levels within these samples were then measured using a sophisticated analysis method known as liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Result and Findings

• For the intravenous (IV) administration, the average plasma concentration of maropitant was found to be 800 ± 140 ng/ml within three minutes of dosage. The elimination half-life, which is the time it takes for the body to reduce the concentration of the drug by half, was calculated as 10.37 ± 2.07 hours. The distribution volume was 6.54 ± 1.84 L/kg.
• For intragastric (IG) administration, the maximum concentration was observed to be 80 ± 40 ng/ml with an elimination half-life of 9.64 ± 1.27 hours. The oral bioavailability, which is the percentage of the administered dose that actively enters the bloodstream, was variable and measured at 13.3 ± 5.3%.

Comparison and Implications

• The levels of maropitant achieved following intragastric administration were comparable to those observed in smaller animals like dogs and cats. However, the concentrations after intravenous administration were lower than in dogs and cats.
• The elimination half-life was longer in horses than in dogs but shorter than in cats. This means the maropitant lasts longer in the horse’s system compared to dogs, but not as long as in cats.
• This research, by determining the pharmacokinetic profile of maropitant citrate in horses, enables a foundation for further studies into the potential of maropitant in treating nausea-related conditions in horses.