Design Characteristics of Inhaler Devices Used for Pulmonary Delivery of Medical Aerosols

For the treatment of respiratory diseases, it is vital to deliver therapeutic doses of drug to specific regions in the Tracheo-Bronchial Tree (TBT) of the lung with maximal efficiency and minimal wastage of medication. Since 19th century many devices have been designed to deliver drugs but the modern era started from 1956 with the introduction of the first metered dose inhaler. These devices can generate aerosols with uniform size distribution, resulting in high deposition in the deep lung which has high surface area (100 m2). Devices that have been commonly used for pulmonary drug delivery are pressurised metered dose inhalers (pMDIs), dry powder inhalers (DPIs) and nebulizers. This review introduces and evaluates the applications of devices used in inhalation therapy and the influence of design characteristics on the delivery of medical aerosols