Pharmacokinetics of intranasal corticosteroids

Topical administration of corticosteroids can reduce the total dose of corticosteroid required to treat the patient and minimize side effects. This logic has led to the development of intranasal corticosteroids (INCS) for allergic and perennial rhinitis. The second generation of these compounds includes beclomethasone dipropionate, budesonide, flunisolide, fluticasone propionate, mometasone furoate, and triamcinolone acetonide. There is evidence that the INCS are effective in rhinitis; however, there is concern about the potential for these compounds to cause growth suppression. In one study, beclomethasone dipropionate significantly reduced growth in children; however, treatment of children with mometasone furoate nasal spray for 1 year showed no signs of growth suppression. It is evident that the differences among INCS lie in their pharmacokinetics. Structural differences among the various INCS influence their metabolism. The goal of INCS therapy is to have a high ratio of topical to systemic activity. The drug delivery device, absorption of the drug, and drug distribution all contribute to effective topical activity of an INCS. In addition, individual drug metabolism and elimination (half-life and drug clearance) also contribute to the therapeutic index of a drug. Overall, the second-generation INCS cause minimal systemic effects at recommended doses.