083 The need for inhalers to have dose counters: an observational study in Edmonton, Alberta, Canada

Objectives Inhalers are first-line treatment for many respiratory conditions including asthma and COPD. A crucial feature of inhalers is the dose counter, allowing individuals to track the number of doses of medicine remaining. Yet, while dry powder inhalers (DPIs) typically have dose counters, many commonly used metered dose inhalers (MDIs) do not. Previous studies suggest that the absence of dose counters in MDIs can result in wasted medication or inhalers being used after they have run out of active medication (i.e., only propellant is left). Our objective was to determine if the absence of dose counters in our setting was associated with MDIs being discarded before all doses of active medication were used, or conversely, being used beyond doses of active medication. Method Inhalers were collected from May 2024–February 2025 (3 pharmacies) as part of our pilot inhaler recycling program in Edmonton, Alberta, Canada. We recorded the type of inhaler and doses of active medication remaining in each inhaler. For the inhalers with dose counters, doses remaining was taken from the dose counter; for the inhalers without dose counters, where published weight/dose relationships were available, the inhalers were weighed and doses remaining were calculated. Inhalers were excluded if they had 80% or more doses remaining, as these inhalers likely were not intended to be fully used. We also excluded inhalers with the active medication inserted for each use (e.g., HandiHaler), inhalers with unreadable dose counters, and inhalers without cannisters. Chi-squared analysis was performed. Results We collected 460 inhalers (33 different types), 368 met the inclusion criteria. All DPIs (212) had dose counters: 89% had nil doses remaining, 3% had 1–10% of doses remaining, and 8% had 11–80% of doses remaining. Among the MDIs with dose counters (36): 6% had negative doses, 61% had nil doses remaining, 8% had 1–10% of doses remaining, and 25% had 11–80% of doses remaining. Among the MDIs without dose counters and published weight/dose relationships (97): 31% had negative doses remaining, 3% had nil doses remaining, 5% had 1–10% of doses remaining, and 61% had 11–80% doses remaining. The difference in the distributions of doses among these groups of inhalers was statistically significant (P<.01). Additionally, there were 23 MDIs without dose counters and no published weight/dose relationship. Conclusion The significant difference in the distribution of doses remaining in inhalers with and without dose counters is concerning. It reinforces previous literature that has consistently shown that dose counters are critical—without dose counters most individuals are either using their MDIs beyond doses of active medication (i.e., only propellant) or discarding them prematurely. These results reinforce the need for regulations that will require MDIs to have dose counters.

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