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How do patients determine that their metered-dose inhaler is empty?
Bruce K Rubin1, Lolly Durotoye
1Department of Pediatrics, Wake Forest University School of Medicine, Medical Center Blvd, Winston Salem, NC 27157, USA. brubin@wfubmc.edu
Chest
|October 16, 2004
Summary
Patients often don't know when their pressurized metered-dose inhaler (pMDI) is empty, leading to overuse. Counting actuations is the only reliable method to determine when to discard pMDI canisters.
Area of Science:
- Pulmonary Medicine
- Pharmaceutical Sciences
- Medical Device Engineering
Background:
- Pressurized metered-dose inhalers (pMDIs) are common drug delivery devices for respiratory conditions.
- Accurate assessment of pMDI canister emptiness is crucial for effective and safe medication use.
Purpose of the Study:
- To investigate how patients determine when pMDI canisters are empty.
- To quantify pMDI depletion under various laboratory conditions.
Main Methods:
- Fifty pediatric asthma patients and their parents were surveyed on pMDI usage.
- pMDI canisters were tested in a laboratory setting to measure the number of actuations.
- Flotation tests and canister shaking were evaluated as methods for determining emptiness.
Main Results:
- 74% of patients were unaware of the number of actuations per canister.
- All patients used inhalers until no sound was heard.
- Both chlorofluorocarbon (CFC) and hydrofluoroalkane (HFA) canisters yielded significantly more actuations than labeled (86% and 52% more, respectively).
- Canister flotation was ineffective; water obstructed valves in 27% of tests.
- Shaking CFC canisters increased actuations, but this effect was not observed with HFA canisters.
Conclusions:
- Patients often continue using pMDIs long after they are empty, potentially doubling the intended medication duration.
- Without dose counters, patients must rely on manually counting actuations to know when to discard a pMDI canister.