Plasma firocoxib concentrations after intra-articular injection of autologous conditioned serum prepared from firocoxib positive horses.
Authors: Ortved K F, Goodale M B, Ober C, Maylin G A, Fortier L A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Firocoxib Carryover in Autologous Conditioned Serum When horses receive oral firocoxib around the time of autologous conditioned serum (ACS) preparation, any residual drug present in the blood could theoretically be concentrated in the final ACS product and subsequently detected systemically following intra-articular injection, potentially resulting in an inadvertent positive drug test. Ortved and colleagues investigated this risk by administering firocoxib (0.1 mg/kg orally, twice at 24-hour intervals) to six horses, then preparing ACS from blood samples collected 4 hours after the second dose, when mean plasma concentrations of firocoxib were 33.3 ng/mL and ACS concentrations were 35.4 ng/mL. Despite these detectable levels in the preparation itself, when 7.5 mL of ACS was injected bilaterally into the tarsocrural joints after the horses had cleared firocoxib systemically, plasma firocoxib concentrations remained below the detection limit (1 ng/mL) at all measured timepoints (0, 4, 8, 12, 24, and 48 hours post-injection). The findings suggest that whilst firocoxib present during ACS preparation does transfer into the final product, the concentration is insufficient to produce detectable systemic levels following intra-articular administration, effectively eliminating this concern for competition horses requiring ACS treatment during active firocoxib therapy or shortly thereafter.
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Practical Takeaways
- •Administering firocoxib to horses at the time of ACS preparation will not result in positive plasma drug tests following intra-articular joint injection, providing reassurance regarding inadvertent contamination
- •Practitioners can safely prepare ACS from horses receiving therapeutic firocoxib without concern for subsequent doping violations in performance horses
- •The rapid clearance of firocoxib (undetectable within 14 days) and minimal systemic absorption from intra-articular ACS injection suggests minimal risk of drug test violations when using this orthobiologic therapy
Key Findings
- •Mean plasma firocoxib concentration was 33.3±4.72 ng/mL at 4h post-dose, with corresponding ACS concentration of 35.4±4.47 ng/mL
- •Firocoxib was undetectable in plasma (LOD 1 ng/mL) in all horses 14 days after the final dose
- •Following intra-articular injection of firocoxib-positive ACS, plasma firocoxib remained below the limit of detection at all timepoints (0, 4, 8, 12, 24, 48h) in all horses
- •ACS prepared from horses with therapeutic firocoxib plasma concentrations does not result in detectable systemic drug levels following intra-articular administration