Floating patterns of metered dose inhalers

Area of Science:

• Pharmaceutical Science
• Biomedical Engineering

Background:

• Metered dose inhalers (MDIs) are crucial for delivering respiratory medications, particularly beta agonists.
• Patients struggle with determining remaining medication in MDIs, impacting compliance and treatment efficacy.
• Existing methods for gauging MDI contents, like dating canisters or counting doses, are often impractical or unreliable.

Purpose of the Study:

• To investigate the float characteristics of commonly used metered dose inhalers as a method for determining remaining medication.
• To establish a reliable and reproducible technique for patients to assess MDI potency.

Main Methods:

• 13 commonly used metered dose inhalers were float-tested in tap water.
• Each inhaler was actuated incrementally to observe changes in buoyancy as contents were depleted.
• Float behavior and canister orientation were recorded at various stages of depletion.

Main Results:

• Prescription-size inhaler canisters generally sink when full and begin to float when approximately one-third of the contents remain.
• Canister orientation changes distinctly as inhalers approach 90% depletion.
• Sample-size canisters exhibited some variability in their floating patterns.

Conclusions:

• The float characteristics of metered dose inhalers provide a reproducible and practical means of gauging remaining medication.
• The pharmaceutical industry should consider including MDI float characteristics in package inserts for patient guidance.
• This method offers a potentially lifesaving tool for patients, especially those using critical medications like beta agonists.