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Process analytical technology (PAT) can be viewed from many perspectives: mathematical, chemical, regulatory, production worker to manufacturing engineer. This technical brief focuses on a high-level perspective.
PAT has grown over the past several decades, driven by the need for improving manufacturing productivity across all industries.1 In the highly regulated pharmaceutical sector, advances are accompanied by worldwide regulatory initiatives, such as the FDA guidance documents on Good Manufacturing Practices, PAT and Quality by Design (QbD), which have influenced agencies including the International Conference on Harmonization.2,3,4 This paradigm shift of the regulatory agencies has promoted the QbD approach for future product submissions and has changed the way companies do business.
Definition of PAT
PAT is used to describe a change in pharmaceutical manufacturing from static batch manufacturing to a more dynamic approach. By definition, PAT is the deployment of instrumentation for real-time, continuous analysis of manufacturing processes and involves use of mathematical modeling (chemometrics) for monitoring chemical and/or physical critical quality attributes (CQAs). PAT is a supplemental technique that allows for detection of events that cannot be derived from conventional discrete variables such as temperature, pressure and flow rate. Effective implementation involves the use of different technologies to support a science-based understanding of the physical, chemical and mechanical properties of the various manufacturing processes. PAT is a testing and feedback loop which allows for process adjustment based upon thorough knowledge of how the components and related processes affect the final product. This is in accordance with the fundamental principle that quality cannot be tested, but should rather be built into the product by design.3Manufacturing QbD in part involves PAT strategies to reduce identified manufacturing risks that are associated with product quality. All of these factors are reflected in product development and process design, and is subject to continual improvements throughout the lifecycle of the product (Figure 1).4
Goal of PAT
The goal of PAT is to design and develop dynamic manufacturing processes that can compensate for variability in both raw materials and equipment in order to consistently ensure a predefined quality at the end of the process. The central objective is to generate product quality information in real-time, in order for current and downstream operations to be adjusted accordingly. PAT aims to ensure that all sources of variability affecting a process are identified, explained and managed.
Aside from content uniformity, NIR can be used for extruder performance verification (residence time distribution studies, process start-up, feeder refill fluctuations, etc). NIR or Raman can be used for assessing polymer layer thickness in multi-polymer systems. Additionally, when the extrusion process is interfaced with Raman, the crystal-form of the drug can be monitored.