Study of caffeine in urine and saliva of horses subjected to urinary acidification.

This research paper investigates the changes in the excretion and saliva secretion patterns of caffeine in racehorses when they’ve been subjected to urinary acidification, a condition that mimics the acidosis following anaerobic exercise. It was found that the urinary pH and kinetic curves for caffeine excretion and secretion were influenced by the presence of urinary acidification.

Introduction and Background

• There has been an increased focus on studying the effects of caffeine in racehorses because it’s deemed to have no valid therapeutic use by the Association of Racing Commissioners International (ARCI).
• The study explores the kinetic alterations in how caffeine is excreted and secreted in saliva of racehorses subjected to urinary acidification, which mimics the effects of acidosis following anaerobic exercise.

Methods and Treatment Groups

• Seven horses were divided into two treatment groups: a control group (SG) and an acidified group (AG).
• SG received 500 ml of saline, followed by 2.0 mg kg(-1) of caffeine intravenously 30 minutes later, while AG received 0.5 g kg(-1) of ascorbic acid to induce urinary acidification, and then 2.0 mg kg(-1) of caffeine intravenously 30 minutes later.
• Urine and saliva samples were collected at various times, from 30 minutes before caffeine administration to 72 hours after.

Results and Observations

• Both groups showed similar kinetic curves for urinary excretion and salivary secretion of caffeine. However, the peak excretion and peak secretion times varied slightly.
• The mean urinary pH for SG was significantly higher than that of AG, validating the successful acidification in the latter group.
• The study suggests that the difference in urine concentration between the two groups might explain the different times for peak excretion and secretion. AG presented less concentrated urine due to increased diuresis.
• Another finding was that despite the different pH levels, the pharmacokinetics of caffeine in the two groups were similar, possibly due to the large difference between the pKa of caffeine and the pH of the medium.

Conclusions

• The study provides valuable insights into caffeine metabolism in racehorses, particularly in the context of how urinary acidification influences its excretion and salivary secretion patterns.
• The results could have implications for developing new rules and guidelines in racing horse management, especially related to caffeine use, and ensuring fair and ethical practices.