[14C]monensin balance in bile-fistulated ponies.

The research study investigates the absorption and elimination of monensin, a type of antibiotic, in ponies with a focus on its presence in the bile, feces, urine, and gastrointestinal tract. The study also explores how monensin metabolizes over time within their system.

Research Methodology:

• Monensin, labeled with Carbon-14 for tracking, was given to two ponies orally and one pony intravenously (iv).
• The dose for oral administration was 1 mg/kg body weight while the iv dose was 8.7 mg.
• The ponies used in this experiment were bile-fistulated, meaning they had a surgical opening made into their bile duct for the purpose of collection and observation.

Finding and Observations:

• For the orally dosed ponies, monensin and its metabolites were primarily eliminated through feces (52% and 69%) and bile (4.7% and 18.3%). Only small amounts were found in urine (<1.7%), and 33% and 7% remained in the gastrointestinal tract after 3 and 4 days respectively.
• The total recovery of the given dose was 90% for one pony and 98% for the other.
• In case of the pony dosed intravenously, a greater percentage of monensin was eliminated in bile (72%), with less in feces (.5%), urine (4.9%) and remaining in the GI tract (15%), all observed after 23 hours.
• Maximum fecal elimination occurred on the third and fourth days for the orally-dosed ponies. The highest biliary elimination observed between 16 and 24 hours for one pony and 48 and 56 hours for the other.
• In the iv-dosed pony, monensin became immeasurable in the plasma within 12 hours after dosing and was detected in bile within 30 minutes.

Conclusions:

• The findings suggest that monensin is primarily eliminated from the body of ponies through feces and bile. Smaller amounts were found in urine and remaining in the gastrointestinal tract post-dosing.
• The absorption and elimination rates of the substance varied amongst individual ponies, and method of administration also impacted the elimination rate.
• The research contributes towards understanding the pharmacokinetics of monensin in ponies. It can provide guidance for using monensin as a medication in veterinary practices, especially regarding appropriate dosing and assessing potential side effects or overdose risk.