ABSTRACT
Relative to other types of drug delivery formulations, pulmonary drug delivery systems have used only a small number of excipients. However, the field is rapidly expanding and the need for alternatives has been realized. Two peaks in patent filings have been identified over the last 30 years (1), both related to the findings by Molina and Rowland (2), which implicated chlorofluorocarbons (CFCs) in the depletion of stratospheric ozone. It became clear that the propellants used in metered dose inhalers (MDIs), the most common device used for administering therapeutic aerosols, would need phasing out and replacement by non-ozone depleting alternatives. Although this transition has largely taken place, the number of excipients available for formulators to use in inhalation aerosol products remains low.
