How patients determine when to replace their metered-dose inhalers.

BACKGROUND: One factor that has been suggested as a possible contributing factor to the rise in asthma morbidity and mortality in the United States is utilization of metered-dose inhalers after the canister has reached its specified maximum number of actuations.
METHODS: We surveyed patients using inhalers as to their awareness of the manufacturer's listed maximum number of actuations for the inhalers they were using, their methods for determining when to replace their inhalers, and the replacement methods they thought were best. We also determined the number of actuations existing in inhalers beyond the specified maximum number listed by the manufacturer, and determined the flotation status of the inhalers after that listed number had been actuated.
RESULTS: Fifty-four percent of patients surveyed were unaware of the specified maximum number of actuations listed by the manufacturer for the inhalers they were currently using. Only 8% reported tallying the number of actuations used. All canisters tested contained a greater number of total actuations than the number listed by the manufacturer. There was no universal flotation status that accurately reflected when these canisters had reached their respective specified maximum number.
CONCLUSIONS: Both lack of knowledge and inhaler replacement practices likely cause patients to extend the use of their metered-dose inhalers beyond the specified maximum number of actuations. This practice may well contribute to the documented rise in asthma morbidity and mortality.