Use of Salbutamol is not a rarity. I have known of several instances.
Common treatment for "Asthmatic " horses.
Administered by..you guessed it...nebuliser.
Whether you can call it therapeutic or whether horses who need it should be racing anyway is open to many viewpoints I guess.
Possibly the connections have beltedly found why the horse hasn't won previously but their timing in this instance was astray.