Wide Variation Found in UK Prescribing Guidance for Preferring Low-Carbon Asthma Inhalers

Understanding if local prescription patterns are influenced by guidance could help policymakers understand what is needed to further encourage a shift to asthma inhalers with less of a climate impact.

Inhalers used for asthma can have an impact on carbon footprint, depending on the type that is used. A recent study sought to identify variation in prescribing guidance in the National Health Service (NHS), which has endorsed the idea of using inhalers that have less impact on the environment, and analyze prescribing data.

Understanding if local prescription patterns are influenced by guidance documents could help policymakers understand what is needed to further encourage a shift to inhalers with less of a climate impact, the researchers noted. Pressurized metered-dose inhalers (MDIs) have a much higher carbon footprint than dry powder inhalers (DPIs) due to propellant gases.

In the United Kingdom, guidance on which inhalers to prescribe in primary care are created by clinical commissioning groups (CCGs) or area prescribing committees. Also in the United Kingdom, 70% of inhaler prescriptions are for MDIs compared with 47.5% in Europe overall.

In its Net Zero report, the NHS supported greater use of low carbon inhalers. In 2000, DPIs were the majority of prescribed inhalers, but by 2020, their share dropped to less than 10%, having been overtaken by MDIs.

To conduct the study, which was published in British Journal of Clinical Pharmacology, the researchers reviewed local CCG adult asthma prescribing guidance for primary care in England in 2019 and recorded DPI and MDI inclusion and analyzed the relationship to prescribing data from OpenPrescribing.net, a platform run by the EBM DataLab at Oxford University.

This study used local guidance documents and not national ones because local ones recommend specific devices. Prescribing guidance was found for 158 of 191 CCGs in England; of the 158, the researchers narrowed the list to 58 unique guidance documents, with some being shared amongst different CCGs.

Each document was checked to see if there was an explicit statement of preferance for one type of inhaler or another. Inhalers were classified by type and dose of medicine, according to treatment pathway, resulting in 5 classes: short-acting beta-agonists (SABAs), low-dose inhaled corticosteroid inhalers (ICS), and low, medium, and high-dose inhalers containing ICS and a long-acting beta-agonist (ICS + LABA).

Of those 58 guidance documents:

  • 12% explicitly preferred MDIs
  • 3% expressed an overall preference for DPIs
  • DPIs were included as first-line recommendations for 77% of SABAs, 78% of ICS, and 90% to 96% for combination (LABA/ICS) inhalers
  • 10% had no DPI included first line for any of the 5 classes examined
  • MDIs were included first line in 98% to 100% in all 3 classes
  • 26% of the guidances had no first-line DPI option for at least 1 asthma management step

The variation in CCGs may have influenced the proportion of inhalers prescribed as MDIs, the authors said.

Although most guidance documents did not state a general preference for device type, for the 15% that did, 3 times as many recommended the high-carbon MDI than DPIs.

Furthermore, MDIs were prescribed more in CCGs that recommended them.

Noting the lack of explicit statements in most CCGs, the authors said the findings suggest that providers "are often steered toward MDI use even in the absence of an explicit overarching device preference."

“Local guidelines still may not be optimised for carbon footprint or patient outcomes and this work provides a method and baseline for further investigation,” the authors said.

They noted that the guidances they examined were from before the COVID-19 pandemic and that since then, some of the guidances have changed.


Twigg AJ, Wilkinson A, Smith JN. Local variation in low carbon footprint inhalers in pre-covid pandemic primary care prescribing guidelines for adult asthma in England and its potential impact. Br J Clin Pharmacol. Published online August 24, 2022. doi.org/10.1111/bcp.15511