Pharmacokinetics of firocoxib after administration of multiple consecutive daily doses to horses.

The research article investigates the behavior of firocoxib, a non-steroidal anti-inflammatory drug, in a horse’s body after multiple doses, through both oral and intravenous administration, by analyzing firocoxib concentrations in urine and plasma.

Research Methodology

The research was conducted in two separate experiments:

• In the first experiment, six healthy female horses, which included five Paint horses and one Quarter Horse, were administered firocoxib orally in the form of a paste for twelve consecutive days. Both urine and plasma samples were collected for analysis.
• In the second experiment, twelve healthy male and female horses were administered intravenous injections of firocoxib for nine consecutive days. In this case, only plasma samples were collected and analysed.

Research Findings

Through an analysis of the collected samples, researchers were able to determine the following:

• The mean clearance and steady-state volume of distribution of firocoxib in the body were determined to be 40.5 mL/h/kg and 2.3 L/kg respectively. These values indicate the rate at which the drug is cleared from the bloodstream and the theoretical volume that would be necessary to contain the total amount of the administered drug at the same concentration that it is present in the blood plasma.
• The mean half-life of the drug was calculated to be around 44.2 hours for intravenous administration and 36.5 hours for oral administration. The half-life of a drug is the period of time required for the concentration or amount of drug in the body to be reduced by one-half.
• The concentration of firocoxib in the urine decreased in parallel with its concentration in the plasma.
• The renal clearance was found to be low (0.26 mL/kg/h) compared to the total body clearance, indicating that the main route of elimination of the drug is through the liver (hepatic clearance), not the kidneys.

Research Conclusions

The researchers concluded that:

• The pharmacokinetics, or how the drug moves through the horse’s body over time, of firocoxib during prolonged use were determined.
• It is possible to use blood plasma or urine to determine drug concentrations in horses. This is because the ratio of drug concentration in plasma to that in urine remained consistent over the time and among different horses.

In essence, this research provides valuable information about how the drug firocoxib behaves in the body of horses over time after multiple doses. It presents a reference for how one might monitor this drug’s concentration in a horse’s body using blood plasma or urine samples.