Pharmacokinetics of intravenously administration of prednisolone in the horse as determined by radioimmunoassay.

The research article describes a study where a radioimmunoassay was developed to determine the pharmacokinetics of the drug prednisolone in horses after it was given intravenously. The study used five adult Thoroughbred horses and studied how the drug was processed over time.

Development of Radioimmunoassay (RIA) for Prednisolone

• A radioimmunoassay (RIA) is a highly sensitive and specific laboratory technique used for measuring the concentration of antigens in body fluids. Here, RIA was developed for prednisolone, a corticosteroid medication, using IgG purified from rabbit antiserum.
• This assay had a sensitivity of detection of 2 ng/ml, indicating that it can accurately identify prednisolone levels as low as 2 nanograms per millilitre in the specimen.
• For specificity, the assay showed cross-reactivity with some substances, but not with naturally occurring steroids like cholesterol, testosterone, estradiol, progesterone or synthetic steroids like betamethasone, methylprednisolone, prednisone, or triamcinolone. This suggests that the assay was relatively specific to prednisolone and is unlikely to give false-positive results due to the presence of these other substances.

Pharmacokinetics of Prednisolone

• In this study, 450 mg of prednisolone sodium succinate was administered intravenously to five adult Thoroughbred horses.
• The RIA technique was then applied to measure prednisolone levels in the horse’s serum. The drug was detected in serum samples for 5 to 7 hours post administration.
• Various pharmacokinetic parameters, such as half-life, excretion constant, volume of distribution, and clearance rate were determined. This gives us a detailed picture of how the drug is metabolized and excreted over time in horses.

Prednisolone Detection in Urine

• The RIA also detected prednisolone in the urine of the horses, beginning one hour post administration. The levels increased significantly after two hours and reached a peak at four hours post administration.
• The urinary levels then decreased until seven hours after administration, at which point they rose again. They finally dropped to minimal detectable levels 48 hours post administration. This indicates that prednisolone was excreted via the urine over a relatively extended period.

In Summary

• The study presents a relatively specific and sensitive RIA for the detection of prednisolone, showing its applicability in determining the pharmacokinetics of the drug in horses, which could be beneficial for veterinary practice and doping control in horse racing.