Spray Pattern and Plume Geometry Measurements of Current and Low GWP Propellants HFA152a and HFO1234ze(E) pMDIs With and Without Ethanol
Holly Dowdle1, Benjamin Myatt1
1Kindeva Drug Delivery, Charnwood Campus, Loughborough, UK
Summary
As the pressurized metered dose inhaler industry is making the switch to lower global warming potential propellants, more understanding is needed on how the new propellants perform in pMDI products using existing characterisation techniques. This study characterises the spray pattern and plume geometry of propellant and propellant with 12% w/w ethanol formulations of the current and new propellants. Standard spray pattern tests at 30 mm, 60 mm and plume geometry in line with industry guidance were performed using an Oxford Lasers EnVision Pharma R&D system. These tests revealed that both HFA134a and HFA152a had the largest spray pattern areas at 30 mm and 60 mm, with HFA227ea having the smallest area, due to the differences in propellant saturated vapour pressure. The spray pattern areas were proportional to vapour pressure at 30 mm distance. However, for HFA152a the plume expanded at a greater rate than that of HFA134a, which could be due to the lower density of HFA152a. When adding ethanol to the propellants, the spray pattern area reduced for most of the propellants and the shot-to-shot variability reduced; this would indicate that adding ethanol stabilises formulations. These results present the need for formulators to understand more about the physical properties of the propellants, so that similar product performance can be achieved when it comes to reformulating with the new propellants.