In-line Fluorescence Spectroscopy for Quantification of Low Amount of Active Pharmaceutical Ingredient.

The pharmaceutical industry is currently implementing new manufacturing principles and modernizing the related processing solutions. A key element in this development is implementation of process analytical technologies (PAT) for measuring product quality in a real-time mode, ideally for a continuously operating processing line. Near-infrared (NIR) spectroscopy is widely used for this purpose, but has limited use for low concentration formulations, due to its inherent detection limit. Light-induced fluorescence (LIF) spectroscopy is a PAT tool that can be used to quantify low concentrations of active pharmaceutical ingredient, and recent development of instrumentation has made it available for in-line applications. In this study, the content of tryptophan in a dynamic powder flow could be measured as low as 0.10 w/w % with LIF spectroscopy with good accuracy of RMSEP = 0.008 w/w %. Both partial least squares regression and support vector machines (SVM) were investigated, but we found SVM to be the better option due to non-linearities between the calibration test and the in-line measurements. With the use of SVM, LIF spectroscopy is a promising candidate for low concentration applications where NIR is not suitable.

High-shear granulation as a manufacturing method for cocrystal granules.

Cocrystal formation allows the tailoring of physicochemical as well as of mechanical properties of an API. However, there is a lack of large-scale manufacturing methods of cocrystals. Therefore, the objective of this work was to examine the suitability of high-shear wet granulation as a manufacturing method for cocrystal granules on a batch scale. Furthermore, the cocrystal granules were characterized regarding their mechanical properties as well as their dissolution behavior. High-shear wet granulation was found to be a feasible manufacturing method for cocrystal granules. Cocrystal formation depended on the exposure time of the solids to the granulation liquid (water), the amount of liquid, the impeller speed of the granulator, and on the excipients (hydroxyl propylcellulose, microcrystalline cellulose, calcium hydrogenphosphate) used in the formulation. Storage stability was strongly influenced by the excipients, since in presence of calcium hydrogenphosphate, the poorly water-soluble salt calcium tartrate monohydrate was formed at high relative humidity. Interestingly, compactability was increased by cocrystal formation compared to that of the reference granules (piracetam and the respective excipients). The drug release was slightly decreased by cocrystal formation, most likely due to the lower solubility of the cocrystal. In the presence of calcium hydrogenphosphate however, no influence of cocrystal formation on either compactability or on drug release were observed, compared with the reference tablets. It was concluded that high-shear wet granulation is a valuable, however complex, manufacturing method for cocrystals. Cocrystal formation may influence compactability and drug release and thus affect drug performance and should be investigated during pre-formulation.

Rapid insight into heating-induced phase transformations in the solid state of the calcium salt of atorvastatin using multivariate data analysis.

PURPOSE: To investigate the heating-induced dehydration and melting behavior of the trihydrate phase of the calcium salt of atorvastatin. METHODS: Multivariate curve resolution (MCR) was used to decompose a variable-temperature synchrotron X-ray powder diffraction (VT-XRPD) data matrix into diffraction patterns and concentration profiles of pure drug phases. RESULTS: By means of the MCR-estimated diffraction patterns and concentration profiles, the trihydrate phase of the drug salt was found to dehydrate sequentially into two partially dehydrated hydrate structures upon heating from 25 to 110°C, with no associated breakage of the original crystal lattice. During heating from 110 to 140°C, the remaining water was lost from the solid drug salt, which instantly collapsed into a liquid crystalline phase. An isotropic melt was formed above 155°C. Thermogravimetric analysis, hot-stage polarized light microscopy, and hot-stage Raman spectroscopy combined with principal component analysis (PCA) was shown to provide consistent results. CONCLUSIONS: This study demonstrates that MCR combined with VT-XRPD is a powerful tool for rapid interpretation of complex dehydration behavior of drug hydrates, and it is also the first report on a liquid crystalline phase of the calcium salt of atorvastatin.

Disproportionation of the calcium salt of atorvastatin in the presence of acidic excipients.

The aim of the present study was to combine vibrational spectroscopy and chemometrics for investigating excipient-induced disproportionation of the calcium salt of atorvastatin into the corresponding free acid form in environments relevant to manufacturing and storage of solid dosage formulations. Of the excipients investigated, citric acid and polyacrylic acid were found to induce disproportionation. Moreover, it was also observed that exposure to high relative humidity, elevated temperatures, and milling all promoted disproportionation. The results suggest that disproportionation of drug salts in powders happens via a solution-mediated mechanism and that the choice of excipient has a considerable impact on the extent of disproportionation observed. Thus, careful attention must be paid to excipient selection during pharmaceutical development and exposure to stresses such as high humidity and mechanical activation should be minimized.

Role of excipients on solid-state properties of piroxicam during processing.

There is a need for an improved process understanding of solid dosage pharmaceuticals. In the present study, Raman spectroscopy together with partial least squares (PLS) regression was used to monitor the solid-state composition of piroxicam during processing in the presence of excipients. It was found that including variable selection in PLS regression offers improved quantitative models in terms of predictive performance, easier interpretation of results and reduced experimental workload relative to full-spectrum PLS regression. By means of the applied interval PLS (iPLS) regression model, it was observed that excipients with high water-absorbing potential (microcrystalline cellulose and hydroxypropyl cellulose) and a water-activity-reducing solvent (ethanol) delayed the onset of monohydrate formation during processing in aqueous environments. An alkalizing excipient (sodium bicarbonate) decreased the onset time of monohydrate formation during wet granulation and decreased the dehydration rate during a drying operation. In this study it is demonstrated that the physical stability of hydrate-anhydrate systems in process environments is complicated by a multitude of factors on both macroscopic level and molecular level, and that variable selection for PLS regression is a valuable tool for screening the effects of excipients on the solid-state properties of pharmaceuticals.