Abstract
A key component of pharmaceutical quality is the physical stability of drug ingredients and products. Physical instability can have a negative impact on efficacy, safety, manufacturability, and shelf life. This includes mechanical degradation, moisture-induced changes, polymorphic transformation, crystallization of amorphous forms, and solid-state phase transitions. Critical Quality Attributes (CQAs), Critical Material Attributes (CMAs), and Critical Process Parameters (CPPs) are identified, along with a design space, as part of Quality-by-Design (QbD), a methodical, risk-based framework for designing robust products and processes that guarantee physical stability. During development and manufacturing, Process Analytical Technology (PAT) provides real-time, in-line, and online tools to monitor and control those attributes. This review connects the QbD risk-based approach, PAT-enabled monitoring and control strategies, and the scientific mechanisms behind physical instability. Discussion topics include case studies, modeling techniques, regulatory context, real-world PAT tools and examples, and future prospects (such as AI/ML-enabled PAT and continuous manufacturing). To protect physical stability, suggestions are given for putting an integrated QbD?PAT strategy into practice.
Keywords
Physical Stability, Quality-by-Design (QbD), Process Analytical Technology (PAT), Polymorphism, Amorphous Stability, Critical Quality Attributes (CQAs), Critical Process Parameters (CPPs), Real-time Monitoring, Modeling and Predictive Approaches
Introduction
The ability of a pharmaceutical product to function as intended over the course of its shelf life is what defines its quality. Physical stability—alterations in the solid-state form, morphology, moisture content, particle size, or mechanical integrity—is just as important as chemical stability, which has long been the focus (e.g., degradation). Physical alterations have resulted in product recalls and can change dissolution, bioavailability, content uniformity, and manufacturability. [1,2]