Switching an asthma patient from a metered dose to a dry powder inhaler significantly reduces their carbon footprint without loss of asthma control, a UK study has shown.

In a post-hoc analysis of a subset of 2,236 patients from the Salford Lung Study in Asthma, researchers found changing from a pressurised metered dose inhaler (pMDI) to a dry powder inhaler (DPI) for maintenance therapy more than halved the per-patient annual carbon footprint for those on the fluticasone furoate/vilanterol (FF/VI) DPI compared with those who continued predominantly with the pMDI (108kg vs 240kg).

The GlaxoSmithKline-funded analysis published in Thorax found switching from pMDI to DPI rescue medications or alternative lower-carbon rescue inhalers, if they became available, would reduce the remaining carbon footprint in the DPI group.

Asthma control improved in both groups, as measured by the Asthma Control Test, but researchers said over the 12-month study period control was superior in the FF/VI DPI group compared with usual care.

The hydrofluorocarbons (HFCs) that replaced banned chlorofluorocarbons (CFCs) in pMDIs did not deplete the ozone layer, but they were potent greenhouse gases, the study authors said.

‘HFC pMDIs account for 3-4% of the total carbon footprint associated with healthcare in the UK, with the majority of emissions associated with the use and disposal of pMDIs rather than their manufacture,’ the study authors wrote.

‘To put this into context, a single dose from an HFC-134a pMDI is approximately equivalent to driving 1 mile in a family car.’

If the approximate 130kg annual saving in carbon footprint per patient shown in the study were scaled up to include all UK adults who use a pMDI for asthma this would represent approximately 40% of the UK’s total carbon footprint due to MDIs, the authors estimated.

The UK was an outlier compared with the rest of Europe with its continued use of pMDIs, they added, noting there were growing calls from government, the NHS, and professional bodies to switch to low carbon-impact inhalers where possible.

‘Together with the role of pharmaceutical companies in producing accessible alternatives, prescribers, pharmacists and patients should be made aware of the significant differences in the global warming potential of different inhalers,’ they wrote.

‘These data indicate that switching from a pMDI to a DPI is an acceptable and worthwhile option for most patients managed in normal everyday practice.’

As previously reported in The Pharmacist, the Primary Care Respiratory Society has called on all calling on all inhaler suppliers to publish the carbon impact of their devices and commit to a rapid transition to low carbon propellants from 2025 onwards.