Cobalt accumulation in horses following repeated administration of cobalt chloride

Abstract

Objective To monitor cobalt concentrations in urine, red blood cells and plasma after chronic parenteral administration of cobalt chloride evaluate these results against the current International Federation of Horseracing Authorities thresholds for detecting cobalt misuse. Design Eight mares were randomly assigned to four treatment groups, with two mares in each group: Group 1 – control group, Group 2 – 25 milligrams cobalt intravenously as CoCl2 weekly, Group 3 – 50 milligrams cobalt intravenously as CoCl2 weekly, and Group 4 – 25 milligrams cobalt intravenously mid‐week and at the end of the week. Urine and blood samples were collected before each weekly administration so that trough levels were assessed. In the group receiving two doses per week, urine and blood were collected prior to the dose given at the end of each week. Samples were initially collected at time zero then weekly for 10 weeks. Three further collections of urine and blood were made at days 81, 106 and 127. Methods Urine creatinine measurements to assess horse hydration status were performed by the Jaffe reaction method. Cobalt determinations in plasma, blood and urine were by inductively coupled plasma—mass spectrometry. Haematocrit concentrations, used to calculate red cell cobalt levels, were performed using a microhematocrit centrifuge. Statistical analyses were conducted in Genstat (v17, VSNi). Results Marked cobalt accumulation was evident with increasing cobalt concentrations for all sample matrices in specimens collected immediately prior to cobalt administration. Correlation between the sample matrices improved when urine cobalt concentration was adjusted for creatinine level. Red cell cobalt levels remained elevated for at least 12 weeks after cessation of administration, consistent with the lifespan of the red cell. There was no significant change in haematocrit concentrations for the duration of the study. Conclusion The current urine cobalt threshold was only effective at detecting acute cobalt exposure while the plasma cobalt threshold was able to consistently identify chronic high‐level cobalt exposure and potential cobalt misuse. The threshold values legislated for urine cobalt do not correlate with those set for plasma. The acute nature of urinary cobalt excretion provides a relatively small window through which cobalt administration is detected. Plasma and red cell cobalt concentrations can provide a clearer picture of potential cobalt misuse.

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

“…Nevertheless, there is evidence of severe organ damage in humans, concerning primarily the gastrointestinal tract, thyroid, heart, and sensory systems, resulting from the intake of inorganic cobalt 118 . For the protection of the impartiality of the sport and the welfare of the animals, confirmatory methods for cobalt quantification by inductively coupled plasma mass spectrometry (ICP‐MS) were published 119–123 . A urinary threshold of 75 ng/mL and a plasma threshold of 2 ng/mL for cobalt in samples from race days or after competition, and a urinary threshold of 2000 ng/mL and a plasma threshold of 10 ng/mL in samples from non‐race days or out‐of‐competition samples, were proposed 120 .…”

“…118 For the protection of the impartiality of the sport and the welfare of the animals, confirmatory methods for cobalt quantification by inductively coupled plasma mass spectrometry (ICP-MS) were published. [119][120][121][122][123] A urinary threshold of 75 ng/mL and a plasma threshold of 2 ng/mL for cobalt in samples from race days or after competition, and a urinary threshold of 2000 ng/mL and a plasma threshold of 10 ng/mL in samples from non-race days or out-ofcompetition samples, were proposed. 120 Currently, the IFHA defined a threshold of 100 ng/mL of total cobalt in urine and 25 ng/mL of total cobalt (free and protein bound) in plasma.…”

Evaluation of cobalt as a performance enhancing drug (PED) in racehorses

“…In the highest two dose groups, 4 mg/kg CoCl (2.4 mg/ kg Co) and 2 mg/kg CoCl (1.2 mg/kg Co) administered weekly for four weeks, horses exceeded the 300 μg/l plasma level for over 50 days, and showed no changes in EPO or haematological effects (Burns et al, 2018). A similar study of chronic Co at doses as high as 25 mg twice weekly over a 42-day period failed to exert any effect on haematocrit of horses, although this dosing regimen also failed to achieve 300 μg/l concentration in plasma (Wenzel et al, 2019).…”

“…While the authors claim that the 75 μg/l urine threshold provides a 1 in 10,315 risk of a false positive test, this would only be true if the underlying distribution were truly lognormal, an assumption that is in question based upon the Kolmogorov-Smirnov normality test employed. The use of urine regulatory thresholds for Co have also been brought into question by a recent study by Wenzel et al (2019), who determined that high urine Co concentrations were most effective at determining an acute Co exposure, rather than Co misuse.…”

“…A single IV dose of 49 mg of Co (Knych et al, 2015) achieved Co plasma concentrations in excess of 300 μg/l for only a few hours. Chronic dosing of about 1000 mg of Co (Burns et al, 2018) increased plasma Co concentrations above 300 μg/l for 50 days, and chronic dosing over 35 days with doses that failed to achieve the 300 ng/ml level (Wenzel et al, 2019) have also been performed. None of these studies demonstrated any effect on red blood cell parameters in the experimental horses, and none of these studies investigated effects of Co on exercise.…”