clenbuterol

noun

clen·​bu·​te·​rol klen-ˈbyü-tə-ˌrȯl, -ˌrōl 

: a sympathomimetic drug used in the form of its hydrochloride C₁₂H₁₈Cl₂N₂O·HCl especially as a bronchodilator in the treatment of asthma

Note: In the U.S., clenbuterol is only approved for veterinary use to treat airway obstruction in horses. Clenbuterol is also used illicitly by athletes to enhance performance (as by increasing muscle mass and aerobic capacity).