Process analytical technology; Process analysers; Film coating; Near-infrared spectroscopy; Raman spectroscopy; Terahertz pulsed imaging; Particle size measurement;OPTICAL COHERENCE TOMOGRAPHY; IN-LINE NIR; PROCESS ANALYTICAL TECHNOLOGY; NEAR-INFRARED SPECTROSCOPY; FLUIDIZED-BED GRANULATION; PARTICLE-SIZE MEASUREMENT; RELEASE COATED PELLETS; RAMAN-SPECTROSCOPY; ACOUSTIC-EMISSION; IMAGE-ANALYSIS

Over the last two decades, regulatory agencies have demanded better understanding of pharmaceutical products and processes by implementing new technological approaches, such as process analytical technology (PAT). Process analysers present a key PAT tool, which enables effective process monitoring, and thus improved process control of medicinal product manufacturing. Process analysers applicable in pharmaceutical coating unit operations are comprehensibly described in the present article. The review is focused on monitoring of solid oral dosage forms during film coating in two most commonly used coating systems, i.e. pan and fluid bed coaters. Brief theoretical background and critical overview of process analysers used for real-time or near real-time (in-, on-, at-line) monitoring of critical quality attributes of film coated dosage forms are presented. Besides well recognized spectroscopic methods (NIR and Raman spectroscopy), other techniques, which have made a significant breakthrough in recent years, are discussed (terahertz pulsed imaging (TPI), chord length distribution (CLD) analysis, and image analysis). Last part of the review is dedicated to novel techniques with high potential to become valuable PAT tools in the future (optical coherence tomography (OCT), acoustic emission (AE), microwave resonance (MR), and laser induced breakdownspectroscopy (LIBS)).