Design Considerations
Inhaler design is also a factor which influences patient compliance. The historical issue for pMDIs was the difficulty that patients have had in coordinating breath inspiration with the timing of the press-and-breathe valve mechanism, which releases the drug dose. A solution to this problem was provided through the introduction of the Autohaler breath-actuated inhaler, which uses the patient’s inspiratory breath to trigger the valve to release the drug dose. Similarly, DPIs rely on patients to activate the release of the dose through inspiration, some of which are passive and rely on the patient inspiratory rate (which has implications of its own), and others include active mechanisms to provide energy for aerosolization. Patients can also have difficulty in understanding how to operate multiple devices.