A review of research methods for elucidating the microstructure of pharmaceutical preparations

The microstructures of pharmaceutical preparations play a pivotal role in determining their critical quality attributes (CQAs), such as drug release, content uniformity, and stability, which greatly impact the safety and efficacy of drugs. Unlike the inherent molecular structures of active pharmaceutical ingredients (APIs) and excipients, the microstructures of pharmaceutical preparations are developed during the formulation process, presenting unique analytical challenges. In this review, we primarily focus on presenting the research methods used to elucidate the microstructures of pharmaceutical preparations, including X-ray imaging (XRI), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, infrared (IR) spectroscopy, and rheometer technology. Subsequently, we highlight the applications, advantages, and limitations of these methods. Finally, we discuss the current challenges and future perspectives in this field. This review aims to provide a comprehensive reference for understanding the microstructures of pharmaceutical preparations, offering new insights and potential advancements in their development.