The β‐agonist clenbuterol in mane and tail hair of horses

Abstract

Summary Reasons for performing study: The β2‐agonist clenbuterol is commonly administered for therapeutic purposes in the horse, but its use an an anabolic agent is illegal. Clenbuterol can be detected in blood and urine for a relatively short period after administration and detection in hair could enhance the analytical range and be used to determine the history of clenbuterol application. Hypothesis: That detection in mane or tail hair is possible over an extended period. Methods: Four horses received 0.8 μg elenbuterol hydrochloride/kg bwt b.i.d. for 10 days. Four other horses were used as untreated controls. Blood, urine, mane and tail hair samples were taken on Day 0 (before) and 5, 10, 30, 35, 40, 60, 90, 120, 150 and 360 days after start of treatment. Gas chromotography/high resolution mass spectrometry (GC/HRMS) was developed for clenbuterol analysis: limit of detection was 0.2 pg/mg; intra‐assay repeatability limit r = 0.06 (confidence level 95%); interassay repeatability limit r = 0.03 (confidence level 95%). Prior to treatment, clenbuterol was absent from all samples analysed. Results: Clenbuterol was detectable as early as Day 5 in tail and mane hair of Segment 1 (0–20 mm from the roots) and was maximal on Day 90. However, as time progressed, shift into lower 20 mm segments was observed. On Day 360, the maximum concentration (up to 21 pg/mg) was located in Segment 13, i.e. 26–28 cm from roots of hair. Clenbuterol was not detectable in blood or urine after Day 30. Mane and tail hair results were very similar. Conclusions: The study showed that the β‐agonist clenbuterol can be found in mane and tail hair of horses after extended periods. Potential relevance: It will be possible to detect clenbuterol in breeding and show horses where anabolic drugs have been used illegally to improve conformation. This method may also be helpful to monitor therapeutic clenbuterol treatment.;

Statistical significance of hair analysis of clenbuterol to discriminate therapeutic use from contamination

“…Clenbuterol is a basic lipophilic compound which binds on the hair pigment melanin. Therefore, a strong and permanent incorporation into hair was reported . In spite of its low therapeutic dosages, single or occasional therapeutic administration permits the detection of clenbuterol in pigmented hair as shown in a previous application study with four horses .…”

Modern Techniques for the Determination of Anabolic–Androgenic Steroid Doping in the Horse

“…If the physical location of a steroid residue in a hair strand can be accurately determined, it should be theoretically possible using the presumed growth rate of the hair to calculate an approximate time of administration. In thoroughbreds, mane hair appears best suited for this purpose, with a steady growth rate of around 2.4 cm/month [50,51]. Less suitable are tail hair, which grows more sporadically, and coat hair, which grows comparatively slowly and with considerable seasonal variation.…”

Determination of ractopamine in animal hair: Application to residue depletion in sheep and residue monitoring

“…Research on agonists found in cattle and human hair has shown that hair can be considered a good matrix to determine the presence of ␤-agonist in living animals [10][11][12][13][14][15]. However, previous studies have focused mainly on clenbuterol, and data regarding the depletion of RAC residues in sheep hair remain inadequate.…”