Environmentally sustainable opportunities for health systems: Metered-dose inhaler prescribing, dispensing, use and waste at a tertiary academic centre.

Background: The Canadian health sector's carbon footprint is among the highest in the world and is responsible for 4.6% of Canada's total greenhouse gas emissions, a quarter of which is linked to pharmaceuticals, with metered-dose inhalers (MDIs) contributing disproportionally high amounts.

Objectives: To describe MDI prescribing, dispensing, use and waste patterns at a Canadian tertiary care academic hospital.

Methods: In a retrospective point-prevalence cohort study, 100 consecutive patients discharged from medical and surgical services who were prescribed at least 1 MDI during their admission were included. Data were collected to describe patient demographics, MDI prescribing, dispensing, use and waste patterns. Use and waste data were applied to annual purchasing data to estimate annual usage and waste. Financial cost was computed using local purchasing estimates and carbon cost was calculated using published estimates.

Results: In 100 consecutively discharged patients, 315 MDIs were dispensed in total, of which 96 were unused. This represents 61,440 actuations dispensed, with 56,773 (92%) of doses unused or wasted. Waste data were applied to annual estimates, with a calculated annual carbon footprint of 315.8 tons of carbon dioxide equivalent (tCO2e). We estimate that a 20% waste reduction would result in carbon savings of 68.5 tCO2e. If 20% of salbutamol prescriptions were switched to the dry powder inhaler alternative, terbutaline, a 14% reduction in waste would be required to offset the additional monetary cost.

Conclusions: This study suggests that 92% of MDI doses are unused and wasted. Opportunities for waste reduction exist and would be associated with both financial and carbon savings.