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Hydrofluoroalkane-philicity: Excipient Screening for Pressurized Metered Dose Inhaler  Formulations

da Rocha S, Conti DS.

RDD Europe 2017. Volume 1, 2017: 143-152.

Abstract:

Excipient screening is an essential step in the development of pressurized metered dose inhaler (pMDI) formulations. In this work, we describe how the combination of calculations from first principles (ab initio) and chemical force microscopy (CFM) is used to understand solvation in hydrofluoroalkanes (HFA), and how a quantitative HFA-philicity scale can be developed from such an atomic/molecular level understanding of the system. We also discuss how such a systematic approach can be used to guide the design of excipients, including dispersing agents and cosolvents, as well as the selection of low global warming potential (GWP) propellants in anticipation of the inevitable phase out of HFAs. These steps may provide for an opportunity to rationally design the next generation pMDIs in contrast with the largely empirical approaches used during the transition from chlorofluorocarbons (CFCs) to HFAs.