This is more convenient for many pet owners than trying to administer daily pills. It makes sense that if constriction is an important feature of this disease that eliminating constriction would be therapeutically helpful. Terbutaline is available for humans as an inhalant but, as mentioned, this is not yet practical for cats. Some veterinarians encourage owners to keep a bottle of injectable terbutaline at home in case of a crisis and show them how to give it. If you are interested in this, let your veterinarian know.
Histamine is an inflammatory substance released during allergic response.
Histamine has been thought to be involved in the airway constriction mechanism and antihistamines are widely prescribed to asthmatic cats. This could be why antihistamines have not been found to be of dramatic assistance in the management of feline asthma. More research in this area is currently needed. One of the biochemicals involved in the asthma inflammation cascade is called serotonin. It is directly involved in constriction of the airways in cats.