Novel hydrofluoroalkane suspension formulations for respiratory drug delivery

Due to the poor solvent properties of hydrofluoroalkanes, suspension is often the only formulation option for respiratory drug delivery. Research in this area has focussed mainly on two main themes over the past 5 years: new design of stabilisers and particle engineering. Among the most important advances, the introduction of secondary particulate systems and the establishment of porous particles as a viable delivery system must be mentioned. Other noteworthy developments include new classes of stabilisers and surface tailoring approaches. Work has been underpinned by new theoretical insights, via the introduction of atomic force microscopy to measure particle interactions, and the development of the surface tension component approach to predict them. Future areas of development include the formulation of nanoparticles and of non-inhalation therapies in non-pressurised hydrofluoroalkanes. All these aspects are reviewed in this article.