Recent developments in dry powder inhalation (DPI) formulations for lung-targeted drug delivery

Background: Dry powder inhalation (DPI) formulations have been widely studied for the treatment of respiratory diseases, including COVID-19, which have become common and dangerous worldwide. Dry powder inhalation formulations have become a popular approach for targeted drug delivery to the lungs. Inhalation offers advantages over other administration routes by providing direct treatment and action to alleviate and manage respiratory conditions. Area covered: This review covers the anatomical and physiological characteristics of the human respiratory tract and the considerations that need to be considered when formulating DPIs. It also provides an overview of current inhalation products and clinical trials in the treatment of respiratory diseases such as asthma, COPD, IPF, PAH, tuberculosis, and COVID-19. Additionally, various methods of particle preparation for DPI formulations are described, including conventional techniques such as milling and spray drying, and novel techniques such as SFD, SCF, TFF, HME, and PRINT. Expert opinion: DPIs are typically prepared by using conventional and novel particle preparation techniques, but these methods may require specialized equipment and have some limitations. Moreover, the number of approved inhalable excipients is limited, which hinders further development of DPI formulations. To address this, the development and approval of new inhalable excipients is needed, and the use of new technologies and excipients is expected to overcome the limitations of DPI formulations.