Enantiomeric composition analysis of pranoprofen in equine plasma and urine by chiral liquid chromatography-tandem mass spectrometry in selected reaction monitoring mode.

The research study describes a new method for analyzing the composition of pranoprofen, a non-steroidal anti-inflammatory drug, in horse plasma and urine using chiral liquid chromatography-tandem mass spectrometry. The aim was to monitor the levels of the two forms of pranoprofen (R-pranoprofen and S-pranoprofen) to help improve doping tests in horses.

Methodology

• The researchers used chiral liquid chromatography-tandem mass spectrometry in selected reaction monitoring mode to analyze the enantiomeric composition of pranoprofen in horse plasma and urine. This is a technique that allows scientists to separate and analyze the different forms of a substance, in this case, the two enantiomers of pranoprofen, R-pranoprofen and S-pranoprofen.
• The concentration ranges for the assay of both enantiomers were 0.001 to 0.1μg/mL for the low range and 0.01 to 1.0μg/mL for the high range. The results demonstrated good precision (RSD≤5.6) and accuracy (RE=-5.3 to 1.9).

Results & Interpretation

• Racemic pranoprofen was orally administered to four horses at a dose of 3.1mg/kg. The researchers found that the plasma concentrations of R-pranoprofen were lower than those of S-pranoprofen from start to finish. This indicates that there may be differences in the way the two forms of pranoprofen are metabolized in horses.
• In contrast, the urinary levels of R-pranoprofen were 2.5 times higher than S-pranoprofen for the first 6 hours, before rapidly decreasing below S-pranoprofen concentration. This suggests that R-pranoprofen is excreted faster than S-pranoprofen, a factor which could impact doping tests in horses.

Conclusion and Significance

• The researchers concluded that monitoring the ratios of R/S pranoprofen in horse urine could be useful for preventing false positives in horse doping tests. This is because the levels of the two enantiomers could vary significantly depending on the time of sample collection, which could potentially lead to erroneous results.
• This study represents an important development in the field of equine sports medicine as it introduces a new method for the detection and monitoring of pranoprofen in horses, which could be crucial for maintaining fair and ethical competitive practices.