Pharmacokinetics of inorganic cobalt and a vitamin B12 supplement in the Thoroughbred horse: Differentiating cobalt abuse from supplementation.

BACKGROUND: While cobalt is an essential micronutrient for vitamin B12 synthesis in the horse, at supraphysiological concentrations, it has been shown to enhance performance in human subjects and rats, and there is evidence that its administration in high doses to horses poses a welfare threat. Animal sport regulators currently control cobalt abuse via international race day thresholds, but this work was initiated to explore means of potentially adding to application of those thresholds since cobalt may be present in physiological concentrations. OBJECTIVES: To devise a scientific basis for differentiation between presence of cobalt from bona fide supplementation and cobalt doping through the use of ratios. STUDY DESIGN: Six Thoroughbred horses were given 10 mL vitamin B12 /cobalt supplement (Hemo-15® ; Vetoquinol, Buckingham, Buckinghamshire, UK., 1.5 mg B12 , 7 mg cobalt gluconate = 983 µg total Co) as an i.v. bolus then an i.v. infusion (15 min) of 100 mg cobalt chloride (45.39 mg Co) 6 weeks later. Pre-and post-administration plasma and urine samples were analysed for cobalt and vitamin B12 . METHODS: Urine and plasma samples were analysed for vitamin B12 using an immunoassay and cobalt concentrations were measured via ICP-MS. Baseline concentrations of cobalt in urine and plasma for each horse were subtracted from their cobalt concentrations post-administration for the PK analysis. Compartmental analysis was used for the determination of plasma PK parameters for cobalt using commercially available software. RESULTS: On administration of a vitamin B12 /cobalt supplement, the ratio of cobalt to vitamin B12 in plasma rapidly increased to approximately 3 and then rapidly declined below a ratio of 1 and then back to near baseline over the next week. On administration of 100 mg cobalt chloride, the ratio initially exceeded 10 in plasma and then declined with the lower 95% confidence interval remaining above a ratio of 1 for 7 days. For two horses with extended sampling, the plasma ratio remained above one for approximately 28 days after cobalt chloride administration. The effect of the administration of the vitamin B12 /cobalt supplement on the urine ratio was transient and reached a peak value of 10 which then rapidly declined. However, a urine ratio of 10 was exceeded, with the lower 95% confidence interval remaining above a ratio of 10 for 7 days after cobalt chloride administration. For the two horses with extended sampling, the urine ratio remained above 10 for about 18 days (442 h) after cobalt chloride administration even though the absolute cobalt urine concentration had dropped below the international threshold of 100 ng/mL after 96 h. MAIN LIMITATIONS: Only one vitamin B12 /cobalt product was evaluated, a limited number of horses were included, the horses were not in full race training and the results may be specific to this population of horses. CONCLUSIONS: The results provide the basis for a potential strategy for allowing supplementation with vitamin B12 products, while controlling the misuse of high doses of cobalt, through a combination of international thresholds and ratios of cobalt to vitamin B12 , in plasma and urine.

Hair analysis as a novel investigative tool for the detection of historical drug use/misuse in the horse: a pilot study.

REASONS FOR PERFORMING STUDY: Analysis of human hair for drug residues is being used increasingly as a diagnostic tool in the investigation of drug use and abuse. Hair analysis is complementary to urine/blood testing in that it can provide an extensive historical record of drug use, is noninvasive, impersonal and can facilitate retesting. However, the technique has not been studied in horses. HYPOTHESIS: That the systemic administration of drugs in horses could be identified by the detection of drug residues in hair. OBJECTIVE: To evaluate hair analysis as a potential retrospective diagnostic test for drug administration in horses by studying the deposition of systemically administered drugs in tail hair. METHODS: Tail hairs (n = 40-50) from 4 horses with known drug histories were washed, chopped into 3-5 mm fragments and extracted overnight, in 0.1 mol/l hydrochloric acid, prior to solid-phase extraction and analysis by high-performance liquid chromatography. Horse 1, a 3-year-old Thoroughbred colt (gastric ulcer), was treated for 14 days with omeprazole; Horse 2, a 3-year-old Thoroughbred colt (anaerobic infection), was treated for 5 days with metronidazole; Horse 3, an 8-year-old Thoroughbred gelding (sinusitis), was treated for 10 days with trimethoprim/sulphadiazine; and Horse 4, a 3-year-old Thoroughbred colt (respiratory infection), was treated for 5 days with procaine benzylpenicillin. RESULTS: Omeprazole was not detected in tail hair. Metronidazole was detected in tail hair at a concentration of 0.57 ng/mg, trimethoprim and sulphadiazine at concentrations of 9.14 and 2.26 ng/mg, respectively, and procaine at a concentration of 1.66 ng/mg. CONCLUSIONS: The data presented suggest that hair analysis may become a useable technique for the retrospective detection of drug administration in horses. POTENTIAL RELEVANCE: This technique could ultimately be used as part of a prepurchase veterinary examination to identify misuse of anti-inflammatory and sedative drugs, in an in-training testing programme to identify use of anabolic agents, or to provide evidence to support post race blood or urine test results. Clearly, more extensive research will be required to evaluate the effectiveness of the technique over a much broader range of drugs.