54 Volume 6; Issue 3 Journal of Clinical and Nursing Research, 2022, Volume 6, Issue 3 http://ojs.bbwpublisher.com/index.php/JCNR ISSN Online: 2208-3693 ISSN Print: 2208-3685 Inhalation Devices and Pulmonary Drug Delivery Sara M Tony 1 , Mohamed EA Abdelrahim 2 * 1 Beni-Suef Specialized Hospital, Beni-Suef, Egypt 2 Clinical Pharmacy Department, Faculty of Pharmacy, Beni-Suef University, Beni-Suef, Egypt *Corresponding author: Mohamed EA Abdelrahim, mohamedemam9@yahoo.com Copyright: © 2022 Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), permitting distribution and reproduction in any medium, provided the original work is cited. Abstract: Inhaled drug delivery is mainly used to treat pulmonary airway disorders by transporting the drug directly to its targeted location for action. This decreases the dose required to exert a therapeutic effect and minimizes any potential adverse effects. Direct drug delivery to air passages facilitates a faster onset of action; it also minimizes irritation to the stomach, which frequently occurs with oral medications, and prevents the exposure of drugs to pre-systemic metabolism that takes place in the intestine and liver. In addition to that, the lung is regarded as a route for transporting medications throughout the entire body’s blood circulation. The type of medication and the device used to deliver it are both important elements in carrying the drug to its target in the lungs. Different types of inhalation methods are used in inhaled delivery. They differ in the dose delivered, inhalation technique, and other factors. This paper will discuss these factors in more detail. Keywords: Pulmonary drug delivery; pMDI, DPI; Nebulizer Online publication: May 12, 2022 (This article belongs to Special Issue: All about Pharmaceutical Drug Interventions, From Inventing the Drug to its Therapeutic Effect on Patient Health) 1. Mechanism of drug accumulation (deposition) in pulmonary airways Three main mechanisms for drug deposition occur in the lungs. The initial mechanism is termed inertial impaction. It is the most common mechanism by which particles deposit in the upper airways. When air passes through the upper respiratory tract, the particle that gains elevated momentum (velocity x mass) seems incapable of coping with the altered track of inspired air. This high velocity causes impaction on the airway walls inside the lungs. Since the probability of impaction is proportional to the particle’s momentum, particles that are larger and moving at a greater speed or have a higher density will exhibit more impaction. Sedimentation is another mechanism for drug accumulation. Once the airflow velocity decreases, particles are deposited downwards due to gravity. This happens when airflow is restricted in the bronchioles and alveoli. The duration the particles spend in these locations determines the percentage of particles deposited by this mechanism. Holding one’s breath after inspiration increases the time the particles remain in these locations, resulting in higher drug deposition in the lungs [1] . “Brownian diffusion’ is the third deposition mechanism. This is most common mechanism for particles smaller than 1 μm because particles smaller than this move by the random bombardment of gas molecules. The likelihood of deposition through diffusion increases when the particle size is smaller, and it is also more common in areas with low or no airflow, such as the alveoli. This mechanism promotes deposition by holding one’s breath after inspiration. Figure 1 is a diagram of the three mechanisms outlined above [1] .