Molecular and clinical pharmacology of intranasal corticosteroids: clinical and therapeutic implications.

Intranasal corticosteroids (INSs) are effective treatments for allergic rhinitis, rhinosinusitis, and nasal polyposis. In recent years, increased understanding of corticosteroid and glucocorticoid receptor pharmacology has enabled the development of molecules designed specifically to achieve potent, localized activity with minimal risk of systemic exposure. Pharmacologic potency studies using affinity and other assessments have produced similar rank orders of potency, with the most potent being mometasone furoate, fluticasone propionate, and its modification, fluticasone furoate. The furoate and propionate ester side chains render these agents highly lipophilic, which may facilitate their absorption through nasal mucosa and uptake across phospholipid cell membranes. These compounds demonstrate negligible systemic absorption. Systemic absorption rates are higher among the older corticosteroids (flunisolide, beclomethasone dipropionate, triamcinolone acetonide, and budesonide), which have bioavailabilities in the range of 34-49%. Studies, including 1-year studies with mometasone furoate, fluticasone propionate, and budesonide that evaluated potential systemic effects of INSs in children have generally found no adverse effects on hypothalamic-pituitary-adrenal axis function or growth. Clinical data suggest no significant differences in efficacy between the INSs. Theoretically, newer agents with lower systemic availability may be preferable, and may come closer to the pharmacokinetic/pharmacologic criteria for the ideal therapeutic choice.