What is the typical weight in grams of a metered-dose inhaler (MDI)?

Weight of Metered-Dose Inhalers (MDIs)

The typical weight of a metered-dose inhaler (MDI) is approximately 28-36 grams, with variations depending on the specific medication, propellant type, and remaining doses.

MDI Physical Characteristics

• Standard metered-dose inhalers contain propellant gases (HFA134a or HFA227ea) that contribute significantly to their weight, with HFA227ea-containing inhalers typically being heavier 1
• MDIs are portable, self-contained aerosol delivery systems that have been designed for convenient patient use for over 35 years 2
• The weight of an MDI is influenced by:
  • Type of propellant (HFA134a vs HFA227ea)
  • Amount of medication remaining
  • Canister design and materials 1

MDI Components Contributing to Weight

• The metal canister containing medication and propellant constitutes the majority of the inhaler's weight 2
• The plastic actuator (mouthpiece) adds minimal weight to the overall device 3
• MDIs with higher-volume canisters or those using HFA227ea propellant (like Flutiform) tend to be heavier, with carbon footprints exceeding 36 kg CO2e per inhaler 1

Clinical Considerations Related to MDI Size and Weight

• The compact size and relatively light weight of MDIs (28-36g) make them more portable than spacers, which are often "large and bulky" 4
• Despite their convenient size and weight, MDIs may deposit as little as 0% of medication in the lungs with poor technique, and no more than 20% even under optimal conditions 4
• For patients who have difficulty handling the standard MDI due to its size or weight, alternatives include:
  • Dry powder inhalers (DPIs), which have different weight characteristics and don't require coordination between actuation and inhalation 3
  • Breath-activated inhalers, which may be easier to use for certain populations 3

Common Pitfalls Related to MDI Use

• Despite their convenient size and weight, only 25% of patients use MDIs correctly, with significantly poorer technique observed in female patients (4% correct use) compared to males (43% correct use) 5
• The small size of MDIs may contribute to coordination difficulties between actuation and inhalation, particularly in elderly patients or those with cognitive impairments 3, 5
• The lightweight design of MDIs may create a false impression of simplicity, whereas proper technique is critical for effective medication delivery 4, 5