Effects of low global warming potential propellants HFA152a and HFO1234ze(E) on the Morphology of Suspension Based Pressurized Metered Dose Inhaler Sprays

The transition to low global warming propellants in pressurized metered dose inhalers (pMDI) [1] introduces a range of challenges for device and formulation design as the new propellants have different physicochemical properties to
those which they replace [2, 3]. One of the many factors influenced by propellant choice is spray plume pattern and geometry [4]. Changes in the targeting angle and spreading rate of the spray can influence mouthpiece and throat deposition as well as aerosol properties [5]. In prior work, it was shown that solution formulations vary in respect of their stability and shot-to-shot repeatability depending on propellant choice, with the cosolvent having a dominant effect [6]. In this work, suspension formulations have been evaluated. The data presented herein show that the presence of suspended particles on mean plume development varies significantly with HFA152a and HFO1234ze(E) propellants when compared to a HFA134a control in matched hardware.