Medical Devices for the Delivery of Therapeutic Aerosols to the Lungs
The last decade has seen developments in all categories of inhaler device. However, the underlying principles of aerosol delivery have changed little.
Despite the numerous designs and configurations that may be employed to generate aerosols in therapeutically useful size ranges and concentrations (Chapters 9-11 and 14), there are only three basic categories of aerosol delivery systems for commercially marketed drug products. These are pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs), and nebulizers. These three classes of devices do not represent optimal delivery systems in terms of their ability to produce monodisperse aerosols that can be precisely dosed in a single breath but rather are examples of delivery systems that achieve minimally acceptable characteristics in a simple, convenient, inexpensive, and portable format. To be acceptable for clinical use, an inhalation delivery system must meet certain criteria:
1. It must generate an aerosol with most of the drug carrying particles less than 10m in size and ideally in the range 0.5-5m, the exact size depending on the intended application.