But while the hydrofluorocarbons that replaced CFCs in pressurized metered-dose inhalers don’t deplete the ozone layer, they are potent greenhouse gases.
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Low-carbon inhalers are predominantly used in Europe. The large carbon footprint caused by the use of hydrofluorocarbon propellants in metered-dose inhalers in the UK is three times that in Europe.
Researchers wanted to compare the potential impact on carbon footprint and symptom control of switching maintenance therapy to a dry powder inhaler and continuing with a metered-dose inhaler containing hydrofluorocarbon propellant.
They carried out a secondary analysis of data from a group of patients who were part of the Salford Lung Study in Asthma. This included a broad range of 4000 patients with asthma who were managing their condition at home and closely reflected routine UK clinical practice.
Adults with asthma on regular maintenance therapy to control their symptoms were randomly assigned to either start using a dry powder inhaler (1081; ‘switch group’) or to continue using a pressurized metered-dose inhaler (1151; ‘usual care’) for 12 months.
Both groups were matched for average age (49) and symptom severity. Symptom control was assessed at the start of the study, and after 12, 24, 40, and 52 weeks using a validated test (Asthma Control Test).
Annual CO2 emissions in kg were calculated for the total number of maintenance (preventer and rescue) inhalers prescribed over the 12 month study period.
Patients were allowed to change inhalers during the study, but most stuck with the type to which they had been assigned: 80% remained on a metered-dose inhaler in the usual care group and 85% remained on a dry powder inhaler in the switch group.
Analysis of the data showed that after a year annual CO2 emissions for each person in the ‘switch’ group were less than half those of the usual care group:108 kg vs 240 kg.
Asthma control improved in both treatment arms during the study period. By week 24, the odds of responding well to treatment in the switch group were around double those of the usual care group, and this difference persisted over the entire 12 months.
As a result, the switchers were prescribed around one less rescue salbutamol metered dose inhaler than those who continued on usual care: 7.2 vs 8. The researchers calculated that the annual carbon footprint saving for each patient in the switch group was 130 kg CO2 emissions.
“Each puff of a [metered dose inhaler] is equivalent to driving 1 mile in a family car, so one inhaler is close to driving 200 miles… but a powdered inhaler is about a twentieth of that,” points out the lead author Professor Ashley Woodcock.
The results of this analysis support the growing calls from official bodies that, where possible, switches… to low carbon-impact alternatives should be sought.
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.
Source: Medindia
