Detection of inhaled salbutamol in equine urine by ELISA and GC/MS2

Salbutamol is a beta-adrenergic agonist that is used in the treatment of asthma in humans and chronic obstructive pulmonary disease in horses. Because of its stimulating and growth promoting properties, it is prohibited by horse racing authorities. Recently a number of adapters (eg Equinehaler) have been designed, allowing the use of metered dose inhalers (MDI) approved for human use. However, information on detection times of salbutamol after administration of salbutamol in therapeutic doses by inhalation is lacking. In this study, 2 mg salbutamol (Ventolin) was administered to four standardbred mares via an MDI with an Equinehaler and urine was collected during 48 h. Quantification of salbutamol in horse urine was done via an overnight beta-agonist ELISA kit. Salbutamol was detected between 1 and 48 h post-administration. Relatively large interindividual variations in the total amount excreted during the first 12 h were noticed. The maximum urinary concentrations varied between 4.6 and 8.1 ng/mL. The total amount excreted within the first 12 h varied between 0.2 and 0.7% of the administered dose. For confirmatory analysis in doping control, a GC/MS(2) method was developed and validated. Analysis was performed on an ion trap instrument after solid phase extraction. The limit of detection was 0.25 ng/mL and was lower than in previously reported methods in human urine.