Dry powder inhaler for pulmonary drug delivery: human respiratory system, approved products and therapeutic equivalence guideline

Pulmonary drug delivery is the promising delivery route to treat not only respiratory diseases but also systemic diseases and has proven as a potential delivery route for complex drugs that cannot be delivered orally. Development of dry powder inhalation systems targets the delivery of fine drug particles to the deep lung surface by a combination of particle deposition and clearance in human respiratory tract. Various dry powder inhalers (DPIs) with their advanced technologies have been proposed and marketed to treat pulmonary diseases such as asthma, chronic obstructive pulmonary diseases, cystic fibrosis and furthermore, systemic diseases such as diabetes and schizophrenia. Bioequivalent therapeutic effects can be derived from generic products that provide additional benefits to the patients and the health care system. Currently, European Medicines Agency (EMA) have established the bioequivalent methods to develop and approve the inhaled products. This review covers the anatomical and physiological characteristics of human respiratory tract to understand the mechanism of drug deposition and clearance. Also, therapeutic areas for both local and systemic treatment, DPI products and their advanced technologies are presented. Finally, European Medicines Agency (EMA) guidelines for inhaled products are presented to demonstrate the therapeutic bioequivalence between generic and reference products. © 2017, The Korean Society of Pharmaceutical Sciences and Technology.