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The Formulator's Guide to Transitioning to Low Global Warming Potential pMDIs

Shur J, Rossi I, Ganley W, Kwok P, Telford R, Price R.

Respiratory Drug Delivery 2022. Volume , 2022: 65-74.

Abstract:

Lower global warming potential (GWP) propellants hydrofluoroalkane (HFA) 152a and hydrofluoroolefin (HFO) 1234ze(E) are two alternative propellants to existing propellants employed in life-saving respiratory medications delivered using pressurized metered dose inhalers (pMDIs). This study aimed to investigate the solubility of active ingredients, suspension stability of micronized materials, fundamental physical properties of aerosols emitted from pMDIs using currently employed propellants and low GWP alternatives. Sedimentation rates of albuterol sulfate were more rapid in HFA 152a and HFO 1234ze(E) compared to HFA 134a. Beclomethasone solubility measurements in HFA 152a suggested the solubility of the active ingredient was three times the level measured in HFA 134a. The net surface charges for all propellants were positive. However, HFO 1234ze(E) generated near-neutral charges of both polarities, with HFO being the least bipolar propellant. Net charge may determine relevant differences in aerosol deposition and, therefore, should drive formulation development approaches. The droplet diameter and velocity for the different propellants fell into multiple groups. Droplets generated by the low GWP propellants were larger at short distances from the actuator compared to droplets generated by HFA 134a and 227ea propellants. This information may help guide the use of excipients to achieve desirable performance of products reformulated using these propellants.