The major pharmacologic actions of the xanthines are inhibition of tissue phosphodiesterases which increases cellular cyclic AMP levels by inhibition of its breakdown and metabolism. The xanthines also are adenosine receptor antagonists.

How do Xanthines work in asthma?

Xanthines inhibit late phase airway reactions induced by allergen or chemical sensitizers. But, they offer little protection against methacholine-, histamine, or allergen-induced immediate bronchoconstriction and any protection seen is unrelated to the extent of the initial bronchodilatation.

How does theophylline work?

Theophylline works by opening the airways in your lungs. It does this by relaxing the muscles and decreasing the response to substances that cause your airways to constrict. This makes it easier for you to breathe.