It has no analgesic or addictive properties. The onset of antitussive action occurs in 15 to 30 minutes after administration and is of long duration. Phenylpropanolamine stimulates both alpha and beta adrenergic receptors, similar to ephedrine. Part of its peripheral action is indirect and is due to the displacement of norepinephrine from storage sites, but it also has a direct effect on the adrenergic receptors. Brompheniramine maleate is a histamine antagonist, specifically an Hi-receptor blocking agent belonging to the alkyl amine class of antihistamines.
Antihistamines appear to compete with histamine for receptor sites on effector cells.