This content is from the BTS/SIGN British guideline on the management of asthma (SIGN 158), 2019.

Metered dose inhalers contain propellants which are liquefied, compressed gases used as a driving force and an energy source for atomisation of the drug. Chlorofluorocarbons (CFCs), which were used originally, are potent greenhouse gases and ozone-depleting substances, and were phased out under the Montreal Protocol. They have been replaced by two hydrofluoroalkane (HFA) propellants: 1,1,1,2-tetrafluoroethane (HFA134a) and 1,1,1,2,3,3,3-heptafluoropropane (HFA227ea), identified as having a high global-warming potential.⁵⁴² As a result of this change, MDIs currently contribute an estimated 3.5% of the carbon footprint of the NHS in the UK.⁵⁴³ The UK has a high proportion of MDI use (70%) compared with the rest of Europe (< 50%) and Scandinavia (10–30%).⁵⁴⁴

Prescribers, pharmacists and patients should be aware that there are significant differences in the global-warming potential of different MDIs and that inhalers with low global-warming potential should be used when they are likely to be equally effective. Where there is no alternative to MDIs, lower volume HFA134a inhalers should be used in preference to large volume or HFA227ea inhalers.

[BTS/SIGN 2019]

Patients should be encouraged to ask the pharmacy they use if they can recycle their used inhalers.

[BTS/SIGN 2019]