The pharmacology of alpha-adrenergic decongestants.

The mechanism by which decongestants produce their action is activation of postjunctional alpha-adrenergic receptors found on precapillary and postcapillary blood vessels of the nasal mucosa. Activation of these receptors by either direct binding of the sympathomimetic agent to the binding site of the receptor, or by the enhanced release of norepinephrine produces vasoconstriction. Such vasoconstriction decreases blood flow through the nasal mucosa and results in shrinkage of this tissue. Decongestants can be administered topically, directly onto the nasal mucosa, or orally. Prolonged topical administration may produce rebound congestion. Oral decongestants can affect the cardiovascular, urinary, central nervous, and endocrine systems. Overdose can produce medically significant increases in blood pressure as well as central nervous system stimulation.