How can we propel MDIs into a more sustainable future?

Hydrofluoroalkane (HFAs), or F-gases, have been used as propellants in metered dose inhalers (MDIs) and other inhalation products for many years. However, due to their high global warming potential (GWP) – 1,430 times that of CO2, the United Nations (UN) has committed to reducing global HFA consumption by 80-85% by 2047, with the aim of slowing global warming (1).

Identifying alternatives

The pharmaceutical industry has been exploring alternatives to standard propellants for use in inhalation drug delivery devices and other medical devices. The two potential “greener” candidates currently being considered are:

• 1,1-Difluoroethane (HFA-152a), which exhibits a GWP of 124
• 1,3,3,3-Tetrafluoropropene (HFO-1234ze(E)), which has a GWP of less than 1 – lower than CO₂

However, transitioning to these “greener” propellants is not as straightforward as simply switching out the old propellant for the new. They have different properties and performance profiles, which means formulations may require redevelopment. Furthermore, MDI device designs may also need to be adjusted to create an effective finished product with an adequate shelf life.

Key considerations to ensure successful adoption

When considering any new propellant for use in a MDI, several factors must be considered:

• Toxicology – it is important to determine whether the propellant is safe for human use and doesn’t affect the drug itself.
• Device – any new propellant must be compatible with the materials that make up the MDI valve and canister to ensure stability and long shelf life.
• Formulation - compatibility with actives and excipients within the formulation.
• Manufacturing – a propellant must not interact with the materials used in the filling line equipment, and there must be careful consideration regarding special handling or storage requirements.
• Commercial – the propellant must be widely available and affordable.  
• Regulatory registration – any new propellant must be approved by regulators, such as the US Food and Drug Administration (FDA) or the EU European Medicines Agency (EMA).

The importance of expert support

Given all these considerations, failure to consider the transition to lower GWP propellants in the short term could add costs in the future, as the supply of HFA propellants becomes restricted and demand for new equipment and infrastructure accelerates.

Working with specialists like Recipharm Inhalation Solutions™ can help future-proof operations. Our dedicated team offers pharmaceutical companies a seamless outsourcing service from early-stage development through to commercial manufacturing for MDIs and other inhalation products. In addition to formulation expertise, we offer in-depth device design and development support through Bespak by Recipharm. 

With such a partnership, pharma companies can continue to deliver high-quality inhaled products to patients as the transition away from HFAs gathers pace.

1. UK Progress on reducing F-gas Emissions Fifth report of session 2017-19 published on 25 April 2018 by authority of the House of Commons