Plasma firocoxib concentrations after intra-articular injection of autologous conditioned serum prepared from firocoxib positive horses.

This study investigates if a commonly used horse medication, firocoxib, could be unintentionally detected after intra-articular injection of autologous conditioned serum (ACS) prepared from horses treated with firocoxib. The results show that firocoxib was not present in detectable amounts after injection, suggesting that this treatment doesn’t risk false-positive drug tests.

Objective and Relevance of the Study

• Orthobiologics like autologous conditioned serum (ACS), prepared from the blood of the same horse, are frequently used to treat joint diseases in horses. These treatments can inadvertently include medications that the horse may have been given at the time the blood was drawn for ACS preparation, leading to false-positive drug tests.
• This study examines if ACS prepared from horses treated with the common NSAID firocoxib could result in an inadvertent positive drug test following intra-articular injection.
• This research is crucial because a positive drug test can have serious implications for competition horses, and understanding any possible sources of contamination is key to maintaining fair competition.

Research Methodology

• A group of six horses underwent firocoxib administration in two doses. Blood was sampled from them four hours after the second dosage, and this blood was used to prepare ACS.
• The concentration of firocoxib in both plasma and ACS was measured using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS).
• Once the horses were confirmed to be firocoxib-free, ACS was injected into their tarsocrural joints. Blood samples were taken at regular intervals thereafter, and the firocoxib concentration was measured.

Results and Interpretation

• The mean plasma concentration of firocoxib after the second dose was found to be 33.3±4.72ng/mL. The mean firocoxib concentration in the ACS was measured at 35.4±4.47ng/mL.
• Two weeks after the final dose of firocoxib, the mean plasma concentration was below the limit of detection in all horses.
• The researchers found that even after the intra-articular injection of ACS, the plasma concentration of firocoxib remained below the detectable limit at all times in all horses. This suggests that ACS generated from horses with therapeutic doses of firocoxib did not contain enough medication to lead to a positive drug test.

Conclusions

• The study concluded that the use of ACS prepared from the blood of firocoxib-treated horses does not pose a risk of inadvertently triggering a positive drug test from detectable firocoxib in the bloodstream after intra-articular administration.
• This finding is important for trainers and vets as it assures them that using ACS therapy in horses being treated with firocoxib will not result in false-positive drug test results.