Which statement best describes a primary difference in how MDIs and DPIs deliver medication?

Which statement best describes a primary difference in how MDIs and DPIs deliver medication?

• A. MDIs rely on patient inspiratory effort; DPIs require a propellant
• B. MDIs require a propellant to aerosolize drug; DPIs rely on patient inspiratory effort to disperse dry powder without propellants
• C. Both MDIs and DPIs rely on external propellants
• D. MDIs are breath-activated; DPIs require coordination

Answer: (B)

The essential distinction is how the aerosol is generated. Metered-dose inhalers use a propellant to create a fine spray when you actuate the device, so the medication is delivered as an aerosol that you inhale. Dry-powder inhalers contain powder and rely on your own inhalation to disperse and aerosolize that powder; there’s no propellant involved, and a sufficient inspiratory flow is needed to achieve proper dispersion and lung deposition. This is why the best description is that inhaler uses a propellant to aerosolize the drug, while a dry-powder inhaler depends on the patient’s inspiratory effort to disperse the powder without propellants.

The essential distinction is how the aerosol is generated. Metered-dose inhalers use a propellant to create a fine spray when you actuate the device, so the medication is delivered as an aerosol that you inhale. Dry-powder inhalers contain powder and rely on your own inhalation to disperse and aerosolize that powder; there’s no propellant involved, and a sufficient inspiratory flow is needed to achieve proper dispersion and lung deposition. This is why the best description is that inhaler uses a propellant to aerosolize the drug, while a dry-powder inhaler depends on the patient’s inspiratory effort to disperse the powder without propellants.