“Salbutamol metabolism how to differentiate oral vs. inhaled administrations: Looking outside the box”

Salbutamol belongs to the class of beta-2-agonists, and its use is prohibited by the WADA if administered for reasons different than the pharmacological treatment of respiratory diseases (i.e. asthma , broncospasm). At present, discrimination between the therapeutic and illicit use of salbutamol is based on concentration thresholds, being the urinary concentration of non-sulfated drug mainly, but not exclusively, related to the administered dose and to the route of administration. Small differences in metabolism can be observed due to the difficulty of avoiding a partial oral administration during inhalation administration where a fraction of the dose is swallowed. It appears that investigation of the location of the majority of salbutamol metabolism is of great interest and may add additional knowledge for better discrimination of salbutamol route of administration.