A push towards more environmentally friendly propellants

Triggered by concerns surrounding global warming due to the consumption of greenhouse gases, the United Nations (UN) countries have committed to phase down global hydrofluoroalkane (HFA) consumption by 80-85% by 2047. This decision will impact the inhalation industry and respiratory healthcare sectors where pressurised metered dose inhalers (pMDIs) utilising HFAs as propellants are widely produced and prescribed. 

In 2017, approximately 50 million inhalers were dispensed in the UK alone. Of these, 70% (35 million) were pMDIs. From a patient compliance perspective, it is critically important to sustain the supply of these devices, since not all patients are able to use other inhalation products due to compromised lung function and breathing capability.  

The HFA propellants currently used to deliver and aerosolise medicines in pMDIs include 1,1,1,2-tetrafluoroethane (HFA-134a) and 1,1,1,2,3,3,3-heptafluoropropane (HFA-227ea). Although the amount of HFAs in these devices is small, the phasing out of their use in other industries could result in limited supply which may create a situation where these products are no longer available to patients. Ensuring the availability of equivalent pMDIs that incorporate new propellants is, therefore, a crucial requirement for the industry. 
Two potential alternative propellants have already emerged, these include 1,1-difluoroethane (HFA-152a) and 1,3,3,3-tetrafluoropropene (HFO-1234ze(E))3. Although currently undergoing full safety evaluations, they have been shown to have a lower Global Warming Potential (GWP) and shorter atmospheric life (AL) compared to existing propellants, and therefore are more environmentally friendly.

Before the industry can go any further, the compatibility between these new propellants and pMDI container closure systems such as cans and valves, as well as compatibility between the propellants and actives, and how to develop a process and scale up manufacturing in a safe way, all need to be determined. By starting to work with these potential propellants and documenting preliminary findings, supply chain partners can begin to establish the next steps to secure supply.

As evaluations progress, it is important that drug developers and manufacturers now start the process of preparing their facilities for these new propellants. Those that put measures in place now will future proof their operations, meaning they can continue bringing MDIs to patients that depend on them.  

Read the full article here, in IPI’s digital magazine, on pages 64-66.