Doping control analysis of lithium in horse urine and plasma by inductively coupled plasma mass spectrometry

Lithium salts are commonly prescribed to treat bipolar disorder in humans. They are effective for the treatment of acute mania and the prophylaxis of manic relapses through long-term use. Although there is no reported legitimate therapeutic use of lithium in horses, its potential mood-stabilizing effect, low cost, and ready availability make lithium salt a potential agent of abuse in equine sports, especially for equestrian competition horses. Lithium can be found in soil, plants, and water, as such it is naturally present in the equine body, thus a threshold is necessary to control its misuse in horses. This paper describes the validation of quantification methods for lithium in equine urine and plasma using inductively coupled plasma mass spectrometry (ICP-MS). Based on a population study of lithium in horse urine and an administration study using a single oral dose of lithium chloride (100 mg) to mimic the daily lithium intake from a diet rich in lithium, a urinary threshold of 5 μg/mL was proposed. Applying this urinary threshold to two other administration studies (a single oral dose of 65 g of lithium chloride, and a single intravenous dose of 2.54 g of lithium chloride), excessive lithium in urine could be detected for 8 days and 2.5 days respectively. The concentrations of lithium in plasma following these three lithium chloride administration trials were also studied. Copyright © 2017 John Wiley & Sons, Ltd.