Hydrofluoroalkane formulations of inhaled corticosteroids for the treatment of asthma.

Current international guidelines for the treatment of asthma advocate inhaled corticosteroids as first-line therapy for persistent symptoms. As chlorofluorocarbon (CFC)-based products are being phased out because of environmental concerns, new inhaler propellants, such as hydrofluoroalkane (HFA)-134a, have been developed. The reformulation of existing corticosteroid compounds into HFA propellants has resulted in two distinct classes of corticosteroid aerosols consisting of HFA suspensions and HFA solutions. The new HFA formulations of flunisolide and beclomethasone dipropionate exist as solutions, whereas HFA preparations of fluticasone propionate, triamcinolone acetonide, and mometasone furoate are formulated as suspensions. HFA suspensions retain the same particle size, deposition, and efficacy profiles as their CFC counterparts. HFA solutions, however, exist as extra-fine aerosols which have been shown to penetrate more effectively into the peripheral regions of the lung. Comparisons of HFA solutions with their CFC counterparts have demonstrated equivalent efficacy when given in smaller doses. The safety profiles of both HFA suspensions and solutions, given at equivalent doses, are comparable to CFC formulations. Increasing evidence suggests that inflammation of the small airways plays an important role in the pathogenesis of asthma. Currently, the clinical implications of long-term treatment of the peripheral lung using an extra-fine inhaled corticosteroid aerosol remain uncertain. Future studies, involving histopathologic and clinical endpoints, will be necessary to determine whether treatment with HFA solutions offers significant advantages over currently available therapies.