Development and use of an enzyme-linked immunosorbent assay to monitor serum and urine acepromazine concentrations in thoroghbreds, and possible changes associated with exercise.

The study describes the development of an improved testing technique (ELISA) for detecting the drug acepromazine (ACP) in horses and investigates if exercise affects how quickly the drug is metabolized.

Methodology

• The authors created an enzyme-linked immunosorbent assay (ELISA) specifically for ACP, a commonly used sedative in horses. This involved using a commercially available antibody and a horseradish peroxidase-conjugated oxime derivative of ACP.
• The experiment was conducted on 12 healthy Thoroughbreds aged between 2 to 8 years. The sample group comprised 5 mares, 5 geldings, and 2 stallions.
• The study was designed as a crossover trial, where horses were put through treadmill exercise to see if physical exertion influenced the concentration levels of ACP in their serum (blood fluid) and urine.
• Each horse was administered a single 25mg dose of ACP via intramuscular injection.

Results

• The ELISA developed in this research was able to detect ACP in concentrations as low as 50 pg/ml in serum and 100 pg/ml in urine, demonstrating its high sensitivity.
• When the ACP was administered, peak serum concentrations (10.5 ng/ml) were registered within 30 minutes. The drug could be identified up to 48 hours later in the serum and up to 120 hours later in urine.
• Suprisingly, physical exertion didn’t significantly alter serum concentrations of ACP. However, drug disappeared quicker from the urine (by 48 hours) of horses who exercised.
• The developed ELISA showed some cross-reactivity with a few other phenothiazines (a class of drugs which ACP belongs to), which might slightly affect its specificity.

Conclusion

• The developed ELISA method offers a fast and sensitive way to measure ACP in equine serum and urine.
• The test’s ability to detect ACP several days after it has been administered should help in detecting and preventing the illicit use of the drug in performance horses.
• Though exercise didn’t significantly affect serum ACP concentration, it expedited the clearance of the drug from urine, indicating that physical activity may influence metabolism. This interesting result opens up for further research within this area.