The Problem with Testing at the End
Traditional pharmaceutical manufacturing is built around the idea of testing finished product. You make a batch, you sample it, you test it, and you decide whether it passes. The problem is that by the time you know a batch is out of specification, you have already used the time, materials, and manufacturing capacity to make it. Rejection at the end of the process is expensive. For complex drug products, it can be catastrophic.
Process analytical technology (PAT) flips that model. Instead of testing the finished product, you monitor the process in real time and make adjustments before problems develop. The batch still gets tested for release, but the data generated during manufacture gives you confidence before you even run the final tests.
The Core PAT Tools in Oral Solid Manufacturing
Near-Infrared Spectroscopy (NIR)
NIR is the most widely implemented PAT tool in tablet manufacturing. It works by shining near-infrared light onto a powder or granule blend and measuring the wavelengths absorbed. Because different chemical bonds absorb at characteristic wavelengths, the resulting spectrum is a fingerprint of the material’s chemical composition. With appropriate calibration models, NIR can measure blend uniformity in real time during mixing, detect the endpoint of a granulation process, and confirm coating uniformity during film coating.
NIR does not require sample preparation or consumables, and it can be implemented as a non-contact measurement that does not disturb the process. Those properties make it well suited to continuous monitoring applications in blending and coating.
Raman Spectroscopy
Raman provides complementary chemical information to NIR and is particularly useful for monitoring polymorphic form in real time. Because different polymorphs of the same API have distinct Raman spectra, a probe positioned in a dryer or granulator can detect whether the solid form is changing during the process. For APIs that are prone to polymorphic conversion under the heat and humidity conditions of wet granulation, real-time Raman monitoring provides a direct safety net.
Particle Size Analysers
Focused beam reflectance measurement (FBRM) uses a scanning laser to measure the chord length distribution of particles in suspension or slurry in real time. In wet granulation, it provides continuous data on how granule size is evolving during the granulation process, allowing the endpoint to be determined from the particle size profile rather than from a fixed time or a grab sample.
PAT in the Regulatory Framework
| Regulatory Document | Relevance to PAT |
| ICH Q8(R2) Pharmaceutical Development | Introduces design space and Quality by Design concepts that PAT supports; encourages understanding of process-property relationships |
| ICH Q10 Pharmaceutical Quality System | Promotes continual improvement; PAT data feeds directly into process monitoring and improvement programmes |
| FDA PAT Guidance (2004) | Established the FDA’s position that PAT is encouraged and that real-time release testing can replace end-product testing where appropriate |
| EMA Reflection Paper on PAT | Aligns with FDA position; supports use of NIR and other inline tools in EU GMP environments |
| ICH Q13 Continuous Manufacturing | PAT is foundational to continuous manufacturing; real-time monitoring required for process control in continuous processes |
Real-Time Release Testing: The Regulatory Endgame
The ultimate application of PAT in pharmaceutical manufacturing is real-time release testing (RTRT): replacing traditional end-product testing with a combination of inline process data and reduced end-product testing that together provide equivalent or greater assurance of product quality. ICH Q8(R2) explicitly supports RTRT as an outcome of Quality by Design development. For blend uniformity in particular, the FDA has accepted NIR-based RTRT as a replacement for conventional powder sampling and HPLC analysis in several approved products.
Implementing RTRT requires robust calibration models, validated PAT methods, and a clearly defined control strategy that specifies how real-time data is used in batch disposition decisions. It is not a shortcut, but it produces better process understanding and more robust manufacturing than conventional end-point testing alone.
PAT Capability at Ardena Ghent
Ardena’s oral solid manufacturing team at Ghent uses PAT tools including NIR spectroscopy and particle size analysis as part of its development and manufacturing programmes. The team has experience developing NIR calibration models for blend uniformity and granulation endpoint determination, and integrating PAT data into the process understanding and control strategy documentation required for CMC regulatory filings.
