Plasma concentrations and urinary excretion of nandrolone and/or its metabolites after intramuscular injection of nandrolone phenylpropionate to horses.

The research study investigates how long it takes for the anabolic steroid nandrolone phenylpropionate to clear from a horse’s system. It was found that the steroid remained detectable for up to five weeks after the final dose, a significant finding for the regulation and monitoring of steroid use in horse racing.

Research Methodology

• The study utilized a radioimmunological method as a screening procedure to determine the clearance time of nandrolone phenylpropionate from horses.
• Seven horses were administered therapeutic doses of the steroid via weekly intramuscular injections. In a separate instance, some horses were given a single dose of the same steroid.

Findings

• The study found that weekly injections kept a high plasma concentration of the steroid in the bodies of the horses.
• The detection period of nandrolone and its metabolites in plasma was around 23 days for resting horses and 20 days for those being exercised.
• The detection period in urine was approximately 25 days for both resting and exercised horses, indicating that physical activity did not significantly alter the clearance time.
• A single dose had a slightly shorter detection period in both plasma and urine of resting horses, approximately 12 and 13 days, respectively.
• There was considerable variation in clearance times among the horses tested, with the time taken for the plasma and urine concentrations to return to pre-dose values being particularly variable in exercised horses.

Implications

• The research results imply that for horses in training, the clearance period for the steroid may be over five weeks, a time frame approaching the minimum of 42 days suggested by the Royal College of Veterinary Surgeons before anabolic steroids’ therapeutic use should be discontinued prior to racing.
• These findings underline the importance of further fiscal research and regulation to prevent the misuse of anabolic steroids in horse racing and preserve the fairness of competition.