Bitolterol is a prodrug that releases colterol on activation by esterases in the lung.
Colterol is a direct-acting agonist, and the N-t-butyl group makes it β2-selective with a binding
potency equivalent to that of isoetharine and terbutaline. The ester form is lipophilic, which helps
to keep it local in the lung and resistant to COMT, which tends to increase its duration of action.
Onset begins 2 to 4 minutes after administration, and the effect can last as long as 8 hours. It
has a adverse effect profile similar to that of other β2-selective agonists, with less drowsiness
and restlessness compared to other direct-acting agonists.
![(tert-butyl)[beta-hydroxy-3,4-bis(p-toluoyloxy)phenethyl]ammonium methanesulphonate](https://www.chemicalbook.com/CAS/GIF/30392-41-7.gif)
