Pathophysiology
While the mechanism of RM is unclear, several theories have been proposed.
Sympathomimetic amines, such as phenylephrine and pseudoephedrine, stimulate both alpha and beta adrenergic receptors. At first, the vasoconstrictive effect of alpha-receptors dominates. This effect fades first, allowing the vasodilation due to beta-receptor stimulation to emerge.
Imidazolamine derivatives, such as oxymetazoline, may participate in negative feedback on endogenous norepinephrine production. Therefore, after cessation of prolonged use, there will be inadequate sympathetic vasoconstriction in the nasal mucosa, and domination of parasympathetic activity can result in increased secretions and nasal edema.
However, if oxymetazoline is used only nightly for allergic rhinitis, it can be used longer than one week without risk of rhinitis medicamentosa.
Read more about this topic: Rhinitis Medicamentosa