Mast cell stabilizers.

The precise mode of action of the well-studied cromolyn sodium and the newer nedocromil sodium has not been completely elucidated. Because the drugs do not pass the cell membrane and enter the cell, they are virtually not metabolized, do not exert a systemic action, and therefore are associated with only minimal systemic toxicity. To be effective either drug must be applied topically and directly to the nasal mucosa. Proper contact with the nasal mucosa is essential for efficacy; in patients with nasal congestion and secretions, vasoconstrictors or saline lavages are indicated before cromolyn or nedocromil use. Both products are highly effective in patients who have IgE-mediated allergic rhinitis but must be administered prophylactically before exposure to an allergen to prevent development of the allergic event. Neither drug is effective in vasomotor rhinitis, exercise-induced rhinitis, or in the management of nasal polyps. Correct diagnosis is essential before therapy.