Breathe Easy: MDI Manufacturers Explore Planet-Friendly Propellants

Millions of people rely on metered dose inhalers (MDIs) to deliver life-saving puffs of medicine to counteract the sudden symptoms of asthma, chronic obstructive pulmonary disease (COPD) and other respiratory conditions.
 
These amazing pocket-sized devices consist of a metal canister containing the medicine, a metering device to ensure the proper dose and an actuator that lets the patient operate the inhaler. A liquified gas propellant, contained in the canister, creates the pressure the MDI needs to dispense the medicine when the user presses the actuator.
 
MDIs have been around since the 1950s, but it’s only in the last several decades that regulators and medical device manufacturers have taken a closer look at conventional propellants through the lens of their environmental impact. Early MDIs used chlorofluorocarbon (CFC) propellants, which have since been banned because they were shown to cause ozone depletion in the Earth’s upper atmosphere.
 
Now most MDIs use hydrofluorocarbons (HFCs). HFCs do not deplete the ozone, but they do cause significant greenhouse gas (GHG) emissions, which contribute to global warming. For example, the commonly used propellent HFC-134a has global warming potential (GWP) of 1,430. That means the release of one kilogram of HFC-134a has a global warming impact equivalent to releasing 1,430 kilograms of carbon dioxide into the atmosphere.
 
The total effect of MDI use on the environment may seem relatively small, but it does mount up, considering the tens of millions of patients who use their inhalers once or more every day. The United Kingdom National Institute for Health and Care Excellence equates a single MDI dose with the release of 500 grams of carbon dioxide equivalent, meaning a 100-dose canister creates the same carbon footprint as a 180-mile car trip.
 
Under the Kigali amendment to the Montreal Protocol, many national governments have committed to phasing out HFC manufacturing and consumption. For example, the United States Environmental Protection Agency (EPA) is on a path to reduce HFC use 85% below the baseline level by 2036, starting with a 10% reduction in 2022. Other countries have set similar goals.
 
As a result, leading pharmaceutical companies, medical product manufacturers and chemical companies are joining forces to explore more planet-friendly propellants. Most promising is a next-generation hydrofluoroolefin (HFO) solution with almost zero global warming impact.
 
Honeywell Solstice Air (HFO-1234ze(E) cGMP) is a near-zero GWP, non-ozone-depleting, non-flammable (per EU-A11 and ASTM E681), volatile organic compound (VOC)-exempt (per U.S. EPA and CARB) propellant in clinical development today for pressurized metered-dose inhalers. The technology has up to 99.9% less GWP than propellants currently used in inhaled respiratory medicines. AstraZeneca, a global leader in the treatment of respiratory diseases such as asthma and COPD, expects their triple-combination therapy Breztri Aerosphere (budesonide/ glycopyrronium/ formoterol fumarate) to be the first medicine to transition to the next-generation propellant, subject to regulatory approval, followed by the rest of their MDI portfolio.
 
These kinds of innovations hold enormous promise as medical device companies look for ways to support their customers’ efforts to reduce their environmental impact without impacting quality of care that is so essential.