Disposition and excretion of flunixin meglumine in horses.

This research article discusses the disposition and excretion of the drug flunixin meglumine in horses. It explores how varying doses of the drug administered intravenously and orally are absorbed, distributed, and eliminated from the body, and how long it takes for the drug to reach its maximum concentration after administration.

Setting and Methodology

• The study investigated the pharmacokinetics of flunixin meglumine, a nonsteroidal anti-inflammatory drug (NSAID) often used in horses to treat pain and inflammation.
• The drug was administered to horses either intravenously (IV) at two different dosages, 1.1 mg/kg and 2.2 mg/kg, or orally at a dosage of 1.1 mg/kg.
• The researchers used both a two-compartment and three-compartment model to describe the disposition of the drug when administered IV, where the compartments likely represent various parts of the body interacting with the drug (such as the blood, tissue, and organs).
• The study also evaluated how much of the drug was eliminated through the urine by measuring urinary recoveries after administration.

Findings

• The IV administration of flunixin meglumine at 1.1 mg/kg could be described by a two-compartment model with half-lives of 0.61 and 1.5 hours.
• When the dosage was increased to 2.2 mg/kg IV, a three-compartment model was deemed more appropriate, with half-lives of 0.16, 1.52, and 6.00 hours.
• A significant proportion of the drug was bound to protein in plasma, suggesting a potential high level of distribution within the body.
• The bioavailability of the drug – how much of it enters the circulation when introduced orally – was found to be 85.8%.
• The drug was excreted quite rapidly, reaching its peak concentration in urine 2 to 4 hours after administration. Cumulative urinary recoveries for IV and oral administrations were 61.0% and 63.3% respectively.

Implications

• The study provides important information about how flunixin meglumine is handled by the body of horses, which can help in determining appropriate dosage and frequency of administration.
• The findings show that flunixin meglumine is rapidly eliminated from the body, and most of the dose is excreted through the urine, which could be taken into account when using the drug in practice.
• The higher bioavailability after oral administration suggests that this route of administration is nearly as effective as IV administration.