Doping Control of Ranitidine in Horses

Area of Science:

• Veterinary Pharmacology
• Equine Sports Medicine
• Analytical Chemistry

Background:

• Ranitidine, a histamine H2-receptor antagonist, is widely used to treat gastric ulceration in horses.
• Previous studies in the early 2000s investigated ranitidine's metabolism and urinary elimination in horses.
• Advancements in technology and the increased use of blood testing for doping control necessitate updated research on ranitidine's detection.

Purpose of the Study:

• To investigate the in vivo metabolism and plasma elimination profile of ranitidine in horses.
• To identify and reinvestigate appropriate targets for controlling the misuse of ranitidine in equine sports.
• To establish elimination profiles for ranitidine and its metabolites in both urine and plasma.

Main Methods:

• Six castrated horses (geldings) were administered Ulcerguard oral paste daily for eight consecutive days.
• The study involved administering specific dosages of ranitidine orally.
• Analysis focused on identifying postulated in vivo metabolites, including ranitidine-S-oxide, ranitidine-N-oxide, desmethylranitidine, and a furoic acid analogue.

Main Results:

• Free ranitidine was detectable in urine for up to 8 days and in plasma for up to 72 hours.
• Two key metabolites, ranitidine-S-oxide and ranitidine-N-oxide, were detected for 8 days in both urine and plasma.
• These metabolites, along with the parent drug, provide evidence of ranitidine's presence and metabolism in horses.

Conclusions:

• Ranitidine-S-oxide and ranitidine-N-oxide are suitable biomarkers for monitoring ranitidine misuse in horses due to their prolonged detection period.
• The established elimination profiles aid in the development of effective doping control strategies for ranitidine in equine athletes.
• This research provides updated data crucial for regulatory bodies and veterinary professionals involved in equine welfare and anti-doping efforts.