Disposition of human drug preparations in the horse. I. Rectally administered indomethacin.

This research paper investigates the rate of absorption and elimination of the drug indomethacin in horses when administered rectally. By using a high-performance liquid chromatographic method, the researchers were able to detect and measure the concentration of indomethacin in horse urine.

Methodology and Procedure

• The strategies employed in this study involve using a complex technique known as high-performance liquid chromatography. This method is utilized to measure the levels of indomethacin in the urine of horses. The method was so refined that the detection of 1 microgram per milliliter of indomethacin in 0.5 ml of horse urine was attainable.
• An important observation was that indomethacin decomposes when urine undergoes alkaline hydrolysis. This fact warrants further inquiry in the paper.

Experimental Results

• In the experiment, two suppositories of a drug known as Indocid, equivalent to 200 mg of indomethacin, were administered rectally to four horses. The findings reveal that indomethacin was rapidly absorbed into the system of horses and remained detectable in their urine, ranging from 1 to 12 hours post-administration.
• The rate at which indomethacin was excreted peaked between 2 to 3 hours, with the maximum concentration varying between 18.5 and 80.6 micrograms per milliliter.

Analysis of Drug Elimination

• Post 12 hours of administering the indomethacin, only 8 to 16% of the given dose was eliminated through urine. This low percentage suggests that the body absorbs a majority of the administered dose and doesn’t eliminate it quickly, therefore such drugs can have longer-lasting effects within the system.
• The researchers also found that a portion of the given dose was excreted as the glucuronide conjugate. Glucuronide conjugation is a major pathway for the biotransformation of many substrates, including drugs, pollutants, bilirubin, bile acids, and steroids. The formation and excretion of glucuronides contribute to the detoxification and elimination of these compounds from the body.

Conclusion

• The paper provides valuable insights into the disposition of human drug preparations in horses, specifically focusing on rectally administered indomethacin. The findings help in understanding how the drug is absorbed and eliminated from a horse’s system and could be crucial in the proper administration and dosage planning of similar drugs in veterinary practice.