Abstract
The World Anti-doping Agency (WADA) has loosened their restrictions towards inhaled β2-agonists. Terbutaline (TER) still requires athletes to provide evidence of asthma to get a dispensation (i.e. TUE) for inhaled use. Limited data exist on the pharmacokinetics of inhaled TER during exercise. The purpose of this study was thus to investigate the influence of exercise in normal and in hot ambient conditions on the pharmacokinetics of 8x500 µg inhaled TER in relation to doping analysis.
Methods: Thirteen trained endurance athletes, all males and non-asthmatics, aged 23.5±4.5 yrs (Mean±SD), VO2max 55.3±7 ml/min/kg, participated in the study. Urine and serum concentrations of TER were determined during three conditions: Exercise (EX), exercise in hot ambient conditions (30-35°C) (EXH), and rest (R). Exercise consisted of submaximal work at 60% of subjects VO2max on a bike ergometer for 124 min, and then a VO2max test. Urine and blood samples were were analyzed for TER.
Results: A significant(P<0.01) interaction (urine specific gravity (USG) x condition x time) was observed for the urine concentrations of TER. USG unadjusted urine concentrations of TER were higher(P<0.05) after 240(1055±256vs.756±144 ng/mL) and 360 min(532±177vs.412±99 ng/mL) compared to adjusted concentrations in EXH, no differences were observed in EX and R. USG unadjusted urine concentrations were higher(P<0.05) during EXH than R after 240 min(1055±256vs.501±411 ng/mL), which also was evident when adjusted for USG(756±144vs.593±219 ng/mL)
Conclusion: Exercise in hot ambient conditions results in higher urine concentrations of TER in trained men. This should be taken into account when evaluating doping cases of TER.
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