Quality by Test was the only way to guarantee quality of drug products before FDA launched current Good Manufacturing Practice. To clearly understand the manufacture processes, FDA generalized Quality by Design (QbD) in the field of pharmacy, which is based on the thorough understanding of how materials and process parameters affect the quality profile of final products. The application of QbD in drug formulation and process design is based on a good understanding of the sources of variability and the manufacture process. In this paper, the basic knowledge of QbD, the elements of QbD, steps and tools for QbD implementation in pharmaceutics field, including risk assessment, design of experiment, and process analytical technology (PAT), are introduced briefly. Moreover, the concrete applications of QbD in various pharmaceutical related unit operations are summarized and presented.

Background In nasal drug delivery system, nasal spray seems to be the most promising delivery method for both local and systemic diseases therapy. Nasal deposition behavior is the most basic and important process for nasal sprays, which is related to nasal mucociliary clearance, retention of a formulation in the nose therefore the therapeutic effect. Area covered The present paper systemically summarized and discussed the factors influencing drug deposition in the nasal cavity upon delivery via nasal sprays, including device, formulation and administration techniques. Emitted dose volume of the device, spray pattern and plume geometry, droplet size distribution and velocity of emitted droplets were important device factors influencing nasal deposition. Besides, viscosity, thixotropic property and surface tension were considered to be the formulation factors influencing nasal deposition of spray. In addition, administration technique influencing nasal deposition included head orientation, administration angle, insertion depth of spray nozzle and breathing profile. Meanwhile, the imaging methods used to predict and visualize the deposition of nasal formulation was illustrated. Expert opinion The review provided important theoretical and experimental knowledge to control the deposition pattern of nasal sprays in order to achieve better therapeutic effect in the clinic.