Improved delivery of inhaled steroids to the large and small airways

Abstract

The reformulation of asthma medications with non-ozone depleting propellants such as hydrofluoroalkane-134a (HFA) has provided the opportunity to apply new knowledge and inhaler technology to improve significantly the delivery of aerosol drugs to the respiratory tract. Beclomethasone dipropionate (BDP), the most commonly prescribed inhaled corticosteroid for asthma therapy, is effective therapy; however currently available chlorofluorocarbon (CFC)-BDP metered dose inhalers typically deliver no more than 10% of the inhaled drug to the lungs with the remainder deposited in the oropharynx. Compared with an average particle size of 3.5-4.0 microns for CFC-BDP, the new HFA-BDP formulation has an average particle size of 1.1 microns and a respirable fraction of approximately 60%. The lung deposition of 99mTc-radiolabelled HFA-BDP has been investigated in healthy volunteers and patients with asthma. Results showed that the HFA-BDP formulation reverses the pattern of distribution seen with CFC-BDP products, delivering most of the dose of inhaled steroid directly to the lungs rather than to the oropharynx and gut where it may lead to unwanted side-effects. As such, HFA-BDP is likely to achieve equivalent efficacy to existing CFC-BDP formulations with lower doses and with reduced potential for local adverse effects.