Control of the misuse of bromide in horses.

This research paper discusses the monitoring of bromide levels in equine plasma and proposes a threshold to control its misuse in competition horses. A more reliable technique, inductively coupled plasma-mass spectrometry (ICP/MS), was used to analyze the samples and confirm high bromide concentrations.

Background and Aim of the Study

• The authors noted the potential misuse of bromide, a sedative hypnotic, in competition horses and thus aimed to develop and validate a reliable method to control its use.
• The study sought to update the previous method, a colorimetric one, which was highly susceptible to matrix interference, with a more dependable method, ICP/MS.

Methodology

• The researchers collected equine plasma and treated it with trichloroacetic acid, a protein precipitant, before diluting it with nitric acid. This prepared sample was directly submitted to ICP/MS analysis.
• Given that bromide occurs naturally in horse plasma, the study also aimed to establish a threshold that indicates misuse. This was based on studies involving 325 horses and considered misuse a risk if it was higher than 1 in 10,000 cases.
• The study suggested further quantification using the ICP/MS standard addition method for samples showing bromide levels over 85 µg/mL.

Results

• The researchers confirmed the presence of bromide through gas chromatography-mass spectrometry (GC-MS) after turning bromide into its pentafluorobenzyl derivative.
• They set a threshold at 90 µg/mL as the level at which a sample is deemed positive for bromide misuse.
• They also took into account a measurement uncertainty of 8 µg/mL at a 99% one-tailed confidence level.
• After administering a dose of potassium bromide to two geldings, the researchers noted plasma bromide levels peaking at approximately 300 µg/mL after about 2 hours and remaining above the set threshold for 8 and 13 days respectively.

Conclusion

• The study offered a more robust method to monitor bromide levels in horse plasma, allowing for better scrutiny and control of its possible misuse in sport horses.