Bioavailability of ketoprofen in horses after rectal administration.

The study focuses on the effectiveness of ketoprofen, a type of non-steroidal anti-inflammatory drug (NSAID), when administered rectally in horses. It compared three different formulations – fatty suppository, hydrophilic suppository, and liquid suspension. The bioavailability of ketoprofen was found to be relatively low, with significant variations between individual horses.

Research Methodology

• The research was conducted on six healthy mares, ages 6 to 12 years, and ranging in weight from 415 to 540 kg.
• The rectal bioavailability of ketoprofen was determined using three different formulations: a fatty suppository, a hydrophilic suppository, and a liquid suspension, each containing 1 gram of ketoprofen.
• Various pharmacological parameters such as elimination half-life, total plasma clearance, volume of distribution, and mean residence time were measured and reported.

Findings and Results

• The average elimination half-life for ketoprofen was observed to be 1.3 hours.
• The total plasma clearance rate was found to be 131.9 mL/min per kg, with a volume of distribution at 255 mL/kg, and the mean residence time was 0.47 hours.
• After rectal administration, the mean maximum plasma ketoprofen concentrations were different for each formulation: 1.6 micrograms/mL for the fatty suppository, 1.1 micrograms/mL for the hydrophilic suppository, and 1.6 micrograms/mL for the liquid suspension.

Overall Bioavailability and Variability

• Despite differences in the concentrations reached, the overall bioavailability of ketoprofen, or the extent to which the drug was absorbed into the body, was relatively low for all three formulations.
• There was significant interindividual variability – 24.5% for the fatty suppository, 28.7% for the hydrophilic suppository, and 31.3% for the liquid suspension.
• The variations between individual horses were not found to be statistically significant (P = 0.05; Friedman test).

Implications of the Findings

• Despite the low bioavailability, there was evidence that the rectally administered formulations were clinically effective, suggesting that this administration route could still provide therapeutic benefits.
• The relatively low bioavailability and the high interindividual variability may suggest a need for dosage adjustment based on each individual horse’s response to treatment.