Terbutaline: level the playing field for inhaled β2-agonists by introducing a dosing and urine threshold
Terbutaline, a short-acting β2-agonist similar to salbutamol, is widely used in Europe in the treatment of asthma and exercise-induced bronchoconstriction. Unlike salbutamol, terbutaline requires therapeutic use exemption (TUE) for therapeutic inhaled use in competitive sport. There is now compelling evidence that supratherapeutic use of terbutaline is performance enhancing, via oral dosing and inhalation. It is likely that the ergogenic effects of terbutaline are class specific for all β2-agonists. The World Anti-Doping Agency (WADA) has introduced dosing and urine threshold and decision limits for other common β2-agonists. This allows athletes to use these drugs for therapeutic purposes while minimising the potential for doping and administrative burden of TUEs. However, no such threshold limits currently exist for terbutaline. For terbutaline, athletes can be granted a TUE, then administer the drug via inhalation at supratherapeutic doses with impunity. The introduction of threshold dosing and urine limits for terbutaline should be a high priority, given the drug's demonstrated ergogenic effects.