A new approach to determine the homogeneity in hyperspectral imaging considering the particle size

Characterization of Pharmaceutical Tablets by X-ray Tomography

Solid dosage forms such as tablets are extensively used in drug administration for their simplicity and large-scale manufacturing capabilities. High-resolution X-ray tomography is one of the most valuable non-destructive techniques to investigate the internal structure of the tablets for drug product development as well as for a cost effective production process. In this work, we review the recent developments in high-resolution X-ray microtomography and its application towards different tablet characterizations. The increased availability of powerful laboratory instrumentation, as well as the advent of high brilliance and coherent 3rd generation synchrotron light sources, combined with advanced data processing techniques, are driving the application of X-ray microtomography forward as an indispensable tool in the pharmaceutical industry.

SEM/EDX and Raman chemical imaging of pharmaceutical tablets: A comparison of tablet surface preparation and analysis methods

A better understanding of a pharmaceutical tablet's microstructure has the potential to unlock the black box between material attributes, process parameters and the critical quality attributes. Microstructure determination requires measuring the spatial-, particle size-distributions (absolute and relative) of the ingredients, and the void space, which is the overt goal of chemical Imaging (CI). Reliable quantitative results can be obtained by imaging multiple layers per tablet, with each layer having a minimal surface roughness. This study utilized scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and Raman chemical imaging (RCI) to provide a comparative discussion of results obtained when determining the microstructure of commercial zinc sulfate tablets, using three methods of tablet surface preparation: scoring & hand-fracturing, microtoming, and grating. A description of the working principles of the measurement and surface preparation methods is followed by a comparison of microstructure (particle size distribution and homogeneity of distribution) using chemical images. A comparison of the general advantages and disadvantages of SEM/EDX and RCI and the common errors in analyzing microstructure are also discussed. The results indicate that in addition to selecting the correct tablet surface preparation method, chemical imaging method, and the subsequent microstructural analyses method, correct problem formulation is also critical.

Near-Infrared Hyperspectral Imaging as a Monitoring Tool for On-Demand Manufacturing of Inkjet-Printed Formulations

This study evaluates the potential use of near-infrared hyperspectral imaging (NIR-HSI) for quantitative determination of the drug amount in inkjet-printed dosage forms. We chose metformin hydrochloride as a model active pharmaceutical ingredient (API) and printed it onto gelatin films using a piezoelectric inkjet printing system. An industry-ready NIR-HSI sensor combined with a motorized movable linear stage was applied for spectral acquisition. Initial API-substrate screening revealed best printing results for gelatin films with TiO₂ filling. For calibration of the NIR-HSI system, escalating drug doses were printed on the substrate. After spectral pre-treatments, including standard normal variate (SNV) and Savitzky-Golay filtering for noise reduction and enhancement of spectral features, principal component analysis (PCA) and partial least squares (PLS) regression were applied to create predictive models for the quantification of independent printed metformin hydrochloride samples. It could be shown that the concentration distribution maps provided by the developed HSI models were capable of clustering and predicting the drug dose in the formulations. HSI model prediction showed significant better correlation to the reference (HPLC) compared to on-board monitoring of dispensed volume of the printer. Overall, the results emphasize the capability of NIR-HSI as a fast and non-destructive method for the quantification and quality control of the deposited API in drug-printing applications.

Process Analytical Technology Tools for Monitoring Pharmaceutical Unit Operations: A Control Strategy for Continuous Process Verification

Various frameworks and methods, such as quality by design (QbD), real time release test (RTRT), and continuous process verification (CPV), have been introduced to improve drug product quality in the pharmaceutical industry. The methods recognize that an appropriate combination of process controls and predefined material attributes and intermediate quality attributes (IQAs) during processing may provide greater assurance of product quality than end-product testing. The efficient analysis method to monitor the relationship between process and quality should be used. Process analytical technology (PAT) was introduced to analyze IQAs during the process of establishing regulatory specifications and facilitating continuous manufacturing improvement. Although PAT was introduced in the pharmaceutical industry in the early 21st century, new PAT tools have been introduced during the last 20 years. In this review, we present the recent pharmaceutical PAT tools and their application in pharmaceutical unit operations. Based on unit operations, the significant IQAs monitored by PAT are presented to establish a control strategy for CPV and real time release testing (RTRT). In addition, the equipment type used in unit operation, PAT tools, multivariate statistical tools, and mathematical preprocessing are introduced, along with relevant literature. This review suggests that various PAT tools are rapidly advancing, and various IQAs are efficiently and precisely monitored in the pharmaceutical industry. Therefore, PAT could be a fundamental tool for the present QbD and CPV to improve drug product quality.

Investigation of the distributional homogeneity on chlorpheniramine maleate tablets using NIR-CI

Homogeneity is the basic element of pharmaceutical analysis. Distributional Homogeneity Index (DHI) was proposed to assess the distributional homogeneity of commercial chlorpheniramine maleate (CPM) tablets. Furthermore, the divergence value of DHI value from expectation DHI (value = 1) was calculated to obtain the CPM distributional homogeneity. The distribution of commercial CPM tablets from six brands was successfully visualized using near infrared chemical imaging (NIR-CI) coupled with characteristic wavenumber method and binary image. Besides, content homogeneity of CPM was obtained through calculating the proportion of white region in the binary image. The result demonstrated that the distributional homogeneity of brand 4 was to be the best among all the brands, following by brand 2, brand 3, brand 5, brand 6 and brand 1. Furthermore, the sequence of the content uniformity was different from the distributional homogeneity, which demonstrated that content uniformity could not represent the distributional homogeneity. This work was a significant method guideline to assess the distributional homogeneity in pharmaceutical field.

Electron microscopy/energy dispersive X-ray spectroscopy of drug distribution in solid dispersions and interpretation by multifractal geometry

Much contemporary research of poorly water-soluble drugs focuses on amorphous solid dispersions (SDs) for oral drug delivery. Recently, a multifractal formalism has been introduced to describe the distribution of an inorganic carrier in SDs. The present work attempts to directly image model drugs by means of scanning electron microscopy and energy dispersive X-ray spectroscopy. The compounds amlodipine, felodipine, glyburide, and indomethacine, which include halogens to enable sufficient scattering in energy dispersive X-ray spectroscopy, were employed to prepare SDs with hydroxypropyl methylcellulose acetate succinate (HPMCAS) by using a microwave method. Following chemical imaging, it was demonstrated that drug distribution was best described by multifractals, which was clearly superior to a monofractal assumption. The obtained fractal dimensions were influenced by drug loading and it was possible to detect microstructural changes upon addition of the plasticizer urea. Accordingly, the multifractal approach bears much potential to better explore the analytical results of chemical formulation imaging. Insights can be gained from the microstructural organization of SDs, which is interesting to further study formulation and process factors as well as physical stability.

PAT: From Western solid dosage forms to Chinese materia medica preparations using NIR-CI

Near-infrared chemical imaging (NIR-CI) is an emerging technology that combines traditional near-infrared spectroscopy with chemical imaging. Therefore, NIR-CI can extract spectral information from pharmaceutical products and simultaneously visualize the spatial distribution of chemical components. The rapid and non-destructive features of NIR-CI make it an attractive process analytical technology (PAT) for identifying and monitoring critical control parameters during the pharmaceutical manufacturing process. This review mainly focuses on the pharmaceutical applications of NIR-CI in each unit operation during the manufacturing processes, from the Western solid dosage forms to the Chinese materia medica preparations. Finally, future applications of chemical imaging in the pharmaceutical industry are discussed.