Propellant Studies

Propellant Testing

Pressurised metered dose inhaler devices (pMDI) are one of the most commonly used devices for the delivery of inhaled therapies to treat chronic respiratory disease. In 1987, the Montreal Protocol prohibited the use of chloroflurocarbons (CFCs), which had historically been used in pMDI’s. These were replaced by hyrdofluorocarbons (HFAs), which whilst not harmful to the ozone layer, still have a high global warming potential (GWP).

To reduce the contribution of pMDI’s to global warming there has been a push within the pharmaceutical industry to develop alternative propellants which are more environmentally friendly. This research is supported by global regulatory agencies with the European Medicines Agency Committee for Medicinal Products for human use (EMA CHMP) recently issuing guideline for assessing orally inhaled products (OIP). This guidance states that “it may be necessary to assess any effect that the new propellant or excipient may have on mucociliary clearance”.

Mucociliary Clearance (MCC) is an essential process in lung physiology whereby cilia clear mucus from airways providing protection from airborne pathogens. Any new propellants must be demonstrated to have no impact on this essential process for healthy lung function. Using radiolabelled inhaled tracers, MCC can be measured with gamma scintigraphy.