Applications of process analytical technology to crystallization processes

Crystallizations of pharmaceutical active ingredients, particularly those that posses multiple polymorphic forms, are among the most critical and least understood pharmaceutical manufacturing processes. Many process and product failures can be traced to a poor understanding and control of crystallization processes. The Food and Drug Administration's process analytical technology (PAT) initiative is a collaborative effort with industry to introduce new and efficient manufacturing technologies into the pharmaceutical industry. PAT's are systems for design, analysis, and control of manufacturing processes. They aim to assure high quality through timely measurements of critical quality and performance attributes of raw materials, in-process materials, and final products. Implementation of PAT involves scientifically based process design and optimization, appropriate sensor technologies, statistical and information tools (chemometrics), and feedback process control strategies working together to produce quality products. This review introduces the concept of PAT and discusses its application to crystallization processes through review of several case studies. A variety of in situ analytical methods combined with chemometric tools for analysis of multivariate process information provide a basis for future improvements in modeling, simulation, and control of crystallization processes.     

振动光谱在药物晶型表征中的应用研究进展

固态药物的多晶型研究对药物质量控制、生产工艺选择、临床疗效评价等发挥重要作用.振动光谱是药物多晶型表征的有力手段之一.本文重点概述了近年来利用傅里叶变换红外(FTIR)光谱技术和拉曼(Raman)光谱技术在活性药物成分(APIs)及药物共晶/盐的多晶型表征中的应用研究进展,阐明两种光谱技术在APIs和药物复合物的晶型分...     

In-line and real-time process monitoring of a freeze drying process using Raman and NIR spectroscopy as complementary process analytical technology (PAT) tools

The aim of the present study was to examine the complementary properties of Raman and near infrared (NIR) spectroscopy as PAT tools for the fast, noninvasive, nondestructive and in-line process monitoring of a freeze drying process. Therefore, Raman and NIR probes were built in the freeze dryer chamber, allowing simultaneous process monitoring. A 5% (w/v) mannitol solution was used as model for freeze drying. Raman and NIR spectra were continuously collected during freeze drying (one Raman and NIR spectrum/min) and the spectra were analyzed using principal component analysis (PCA) and multivariate curve resolution (MCR). Raman spectroscopy was able to supply information about (i) the mannitol solid state throughout the entire process, (ii) the endpoint of freezing (endpoint of mannitol crystallization), and (iii) several physical and chemical phenomena occurring during the process (onset of ice nucleation, onset of mannitol crystallization). NIR spectroscopy proved to be a more sensitive tool to monitor the critical aspects during drying: (i) endpoint of ice sublimation and (ii) monitoring the release of hydrate water during storage. Furthermore, via NIR spectroscopy some Raman observations were confirmed: start of ice nucleation, end of mannitol crystallization and solid state characteristics of the end product. When Raman and NIR monitoring were performed on the same vial, the Raman signal was saturated during the freezing step caused by reflected NIR light reaching the Raman detector. Therefore, NIR and Raman measurements were done on a different vial. Also the importance of the position of the probes (Raman probe above the vial and NIR probe at the bottom of the sidewall of the vial) in order to obtain all required critical information is outlined. Combining Raman and NIR spectroscopy for the simultaneous monitoring of freeze drying allows monitoring almost all critical freeze drying process aspects. Both techniques do not only complement each other, they also provided mutual confirmation of specific conclusions. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3430–3446, 2009     

Determination of amorphous content in the pharmaceutical process environment

The amorphous state has different chemical and physical properties compared with a crystalline one. Amorphous regions in an otherwise crystalline material can affect the bioavailability and the processability. On the other hand, crystalline material can function as nuclei and decrease the stability of an amorphous system. The aim of this study was to determine amorphous content in a pharmaceutical process environment using near infrared (NIR) and Raman spectroscopic techniques together with multivariate modelling tools. Milling was used as a model system for process-induced amorphization of a crystalline starting material, alpha-lactose monohydrate. In addition, the crystallization of amorphous material was studied by storing amorphous material, either amorphous lactose or trehalose, at high relative humidity conditions. The results show that both of the spectroscopic techniques combined with multivariate methods could be applied for quantitation. Preprocessing, as well as the sampling area, was found to affect the performance of the models. Standard normal variate (SNV) transformation was the best preprocessing approach and increasing the sampling area was found to improve the models. The root mean square error of prediction (RMSEP) for quantitation of amorphous lactose using NIR spectroscopy was 2.7%, when a measuring setup with a larger sampling area was used. When the sampling area was smaller, the RMSEPs for lactose and trehalose were 4.3% and 4.2%, respectively. For Raman spectroscopy, the RMSEPs were 2.3% and 2.5% for lactose and trehalose, respectively. However, for the optimal performance of a multivariate model, all the physical forms present, as well as the process environment itself, have to be taken into consideration.     

From laboratory to pilot plant: The solid-state process development of a highly potent cathepsin S/K inhibitor

The solid-state development for the low dose drug molecule SAR114137, a selective and reversible inhibitor of cysteine cathepsin S/K, is reported. Six polymorphic forms as well as various solvate phases were discovered by an extensive polymorphism screening. The solid phase characterizations revealed that phase 1, from which a single crystal structure could be obtained, is the thermodynamically most stable form and therefore it was chosen for pharmaceutical development. The successful scale-up from development laboratory into pilot plant for the crystallization and drying processes is presented. Testing of different drying techniques, like agitated drying in conical or filter dryers as well as spray drying, proved them to be very promising alternatives to the conventional tray drying process and might be used during the industrialization phase of the project. The use of online analytical tools (e.g., Raman spectroscopy) for a better process understanding and as tools for process optimization is shown. Furthermore, wet milling by ultrasound was performed on laboratory scale and discussed as potential option to reach the desired particle size distribution necessary for a good content uniformity of the API in an oral formulation.     

Solid state investigation and characterization of the polymorphic and pseudopolymorphic forms of indapamide

Solid state investigation and polymorphic screening of indapamide, a diuretic drug generally used for the treatment of hypertension was carried out. Substantial differences were obtained in the solid state properties of crystals confirming the existence of a polymorphic and three pseudopolymorphic forms of indapamide. Detailed methods of preparation of the polymorphs and pseudopolymorphs are described. X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed for the characterization of different crystalline forms of indapamide. The stoichiometric ratio of solvents associated with the drug molecules in the pseudopolymorphic forms were calculated using TGA, nuclear magnetic resonance (NMR) spectroscopy and headspace gas chromatographic (HS-GC) analysis.     

Multivariate data analysis as a fast tool in evaluation of solid state phenomena

A thorough understanding of solid state properties is of growing importance. It is often necessary to apply multiple techniques offering complementary information to fully understand the solid state behavior of a given compound and the relations between various polymorphic forms. The vast amount of information generated can be overwhelming and the need for more effective data analysis tools is well recognized. The aim of this study was to investigate the use of multivariate data analysis, in particular principal component analysis (PCA), for fast analysis of solid state information. The data sets analyzed covered dehydration phenomena of a set of hydrates followed by variable temperature X-ray powder diffractometry and Raman spectroscopy and the crystallization of amorphous lactose monitored by Raman spectroscopy. Identification of different transitional states upon the dehydration enabled the molecular level interpretation of the structural changes related to the loss of water, as well as interpretation of the phenomena related to the crystallization. The critical temperatures or critical time points were identified easily using the principal component analysis. The variables (diffraction angles or wavenumbers) that changed could be identified by the careful interpretation of the loadings plots. The PCA approach provides an effective tool for fast screening of solid state information.     

Fourier transform infrared study of protein secondary structural changes in the muscle of Labeo rohita due to arsenic intoxication

Protein is one of the most important nutrients in human diets and fish has become an increasingly important source of protein in most of the developing countries. Among the various fish tissues, muscle is the major contributor of proteins and the whole mass of the body. The goal of this study is to assess the changes in the biochemical compositions in general, and the protein structural changes in particular, in the muscle of Labeo rohita fingerlings due to arsenic intoxication using Fourier transform infrared (FT-IR) spectroscopy. The results of the present study indicate that arsenic intoxication induces significant alteration in the major biochemical compositions such as proteins, lipids and nucleic acids of Labeo rohita. Further, the results clearly indicate considerable change in the composition of muscle proteins due to arsenic intoxication. It is therefore concluded that FT-IR spectroscopy can be a successful detection tool in toxicological research.     

Advances in multivariate analysis in pharmaceutical process development

In the last five years, reports of the application of multivariate methods in pharmaceutical process research and development have burgeoned. Examples range from the widespread adoption of statistical experimental design for screening and process optimization to the implementation of workflows that integrate multivariate characterization, experimental design and the development of quantitative structure-property relationships. Having learned from the application of these techniques in drug discovery and armed with modern high-throughput experimentation platforms, practitioners are discovering the power of experimental design and multivariate methods for shortening process development timelines.     

Applications of NIR spectroscopy to monitoring and analyzing the solid state during industrial crystallization processes

Fiber-optic near infrared (NIR) spectroscopy was used to investigate several key features of the polymorphic transitions observed during the crystallization and the filtration of SaC, an Active Pharmaceutical Ingredient (API) produced by Sanofi-Synthelabo. Using few samples, the spectroscopic data were calibrated to provide measurements of the polymorphic composition of the solid product which is likely to appear in two crystalline forms or in the amorphous state. Both qualitative and quantitative methods were successfully evaluated to characterize the API. The NIR spectroscopy measurement was then applied to investigate the kinetic behavior of the phase transition phenomena against various operating conditions. From the viewpoint of industrial process development several applications are presented. The effects of temperature and seed crystal habits on the rate of transition of filtration cakes are briefly investigated; and a study of the effect of residual water in the solvent on the transition occurring during filtration is more deeply analyzed. The experimental results demonstrate that highly valuable information can be provided by the NIR spectroscopy measurements, when one aims at understanding more deeply and optimizing the consequences of various and complex phenomena involved during the solid processing chain.     

New perspectives for the on-line monitoring of pharmaceutical crystallization processes using in situ infrared spectroscopy

Chemists and engineers involved in the industrial production of solid drugs have to deal with difficult new challenges, including the on-line mastery of the crystal habits and size distribution, the control of polymorphic transitions or the improvement of the chemical purity. A major limitation to improving the control of industrial crystallizers lies in the lack of versatile, accurate and reliable on-line sensors. It is shown that supersaturation measurements can be performed using in situ ATR mid-infrared spectroscopy thus providing valuable real-time information about the crystallization process. Several case studies are presented to illustrate new potential applications of the technique. The reported experimental results outline recent advances in the acquisition of key data characterizing the solute/solvent system in question (i.e. solubility, metastability, phase transformations...), the design of on-line control strategies capable of improving both the crystal size distribution (CSD) and the reproducibility of the quality of the final product, the assessment of improved operating strategies (e.g. seeding batch crystallizers), and the monitoring of polymorphic transitions during cooling crystallization operations. The possibility of evaluating on-line the process impurities, which could allow the reduction of batch-to-batch variations of the quality of the solid product, is also briefly envisaged.     

Rapid determination of vitamin C by NIR,MIR and FT-Raman techniques

Rapid spectroscopic determination of vitamin C in food and pharmaceutical products using infrared and Raman techniques was proposed. In this study, near-infrared (NIR), Fourier transform near-infrared (FT-NIR), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), diffuse reflectance (DRIFTS), Fourier transform infrared-photoacoustic (FTIR-PAS) and FT-Raman spectroscopy were used in conjunction with partial least squares (PLS) regression to quantify vitamin C in powdered mixtures and solutions. Results indicate that the methods adopted have high prediction correlation. R2 values were 0.999 for FTIR-ATR, 0.976 for DRIFTS, 0.966 for FTIR-PAS, 0.988 for NIR, 0.992 for FT-NIR and 0.95 for FT-Raman, with an overall prediction error of 0.2-3.0%. The time required to complete an experiment ranged from 5 s (NIR) to 3 min (FT-Raman). The FTIR and FT-Raman techniques can be complementary tools for qualitative and quantitative characterization of the samples. Infrared and Raman techniques can be used to quantify vitamin C in foods and pharmaceutical products.     

In-line monitoring and interpretation of an indomethacin anti-solvent crystallization process by near-infrared spectroscopy (NIRS)

PAT (process analytical technology) has been emphasized as one of key elements for the full implementation of QbD (quality-by-design) in the pharmaceutical area. NIRS (near-infrared spectroscopy) has been studied intensively as an in-line/on-line monitoring tool in chemical and biomedical industries. A precise and reliable monitoring of the particle characteristics during crystallization along with a suitable control strategy should be highly encouraged for the conformance to new quality system of pharmaceutical products. In this study, the anti-solvent crystallization process of indomethacin (IMC) was monitored using an in-line NIRS. IMC powders were produced via anti-solvent crystallization using two schemes; ‘S-to-A’ (solvent-to-antisolvent) and ‘A-to-S’ (antisolvent-to-solvent). In-line NIR spectra were analyzed by a PCA (principal component analysis) method. Although pure α-form IMC powder was resulted under A-to-S scheme, a mixture of the α-form and γ-form was produced for S-to-A case. By integrating the PCA results with off-line characterization (SEM, XRD, DSC) data, the crystallization process under each scheme was elucidated by three distinct consecutive steps. It was demonstrated that in-line NIRS, combined with PCA, can be very useful to monitor in real time and interpret the anti-solvent crystallization process with respect to the polymorphism and particle size.     

Physical stability and recrystallization kinetics of amorphous ibipinabant drug product by fourier transform raman spectroscopy

The solid-state physical stability and recrystallization kinetics during storage stability are described for an amorphous solid dispersed drug substance, ibipinabant, at a low concentration (1.0%, w/w) in a solid oral dosage form (tablet). The recrystallization behavior of the amorphous ibipinabant-polyvinylpyrrolidone solid dispersion in the tablet product was characterized by Fourier transform (FT) Raman spectroscopy. A partial least-square analysis used for multivariate calibration based on Raman spectra was developed and validated to detect less than 5% (w/w) of the crystalline form (equivalent to less than 0.05% of the total mass of the tablet). The method provided reliable and highly accurate predictive crystallinity assessments after exposure to a variety of stability storage conditions. It was determined that exposure to moisture had a significant impact on the crystallinity of amorphous ibipinabant. The information provided by the method has potential utility for predictive physical stability assessments. Dissolution testing demonstrated that the predicted crystallinity had a direct correlation with this physical property of the drug product. Recrystallization kinetics was measured using FT Raman spectroscopy for the solid dispersion from the tablet product stored at controlled temperature and relative humidity. The measurements were evaluated by application of the Johnson-Mehl-Avrami (JMA) kinetic model to determine recrystallization rate constants and Avrami exponent (n = 2). The analysis showed that the JMA equation could describe the process very well, and indicated that the recrystallization kinetics observed was a two-step process with an induction period (nucleation) followed by rod-like crystal growth.     

Solid-state study of mepivacaine hydrochloride

Different crystalline forms of the local anaesthetic mepivacaine hydrochloride (MH) were revealed by Fourier transform infrared spectroscopy (FT-IR), not by conventional differential scanning calorimetry (DSC). The existence of two polymorphic anhydrous modifications was discovered and further characterized by X-ray powder diffraction and thermal analysis: Form II, the commercial one, and the more stable Form I, obtained by re-crystallization from Form II. Two pseudopolymorphs were also obtained: Form III, a solvate crystallized from ethanol and Form IV, a solvate crystallized from methanol. Single crystal X-ray diffraction data for both solvates were collected and their structures were determined. Form II, metastable and monotropically related to Form I, generates through desolvation of Form III, very often present in industrial processing, where crystallization from ethanol solution is a common practice. For the sake of clarity, the presence of polymorphic forms should be reported in the drug master files of MH. However, since MH is readily water soluble, the observed polymorphism has no relevance to its typical clinical use as aqueous solutions.     

两性霉素B分离纯化工艺研究

本文开发了一种高纯度两性霉素B的分离纯化工艺,通过工艺参数精细化控制,探索了两性霉素B的溶出率和乙醇加入量、溶液pH的关系,将陶瓷膜超滤技术应用于浸泡液处理,以及表面活性剂甘油应用于结晶体系,并确定了结晶的最佳pH值,本方法制备的两性霉素B结晶粉的生物效价检测含量大于970u/mg,面积归一百分含量大于95%,杂质含量低,产品质量优于同行业产品。 本工艺稳定,流程简单,便于规模化生产。     

两性霉素B分离纯化工艺研究

本文开发了一种高纯度两性霉素B的分离纯化工艺,通过工艺参数精细化控制,探索了两性霉素B的溶出率和乙醇加入量、溶液pH的关系,将陶瓷膜超滤技术应用于浸泡液处理,以及表面活性剂甘油应用于结晶体系,并确定了结晶的最佳pH值,本方法制备的两性霉素B结晶粉的生物效价检测含量大于970u/mg,面积归一百分含量大于95%,杂质含量低,产品质量优于同行业产品。     

In line NIR quantification of film thickness on pharmaceutical pellets during a fluid bed coating process

Along with the risk-based approach, process analytical technology (PAT) has emerged as one of the key elements to fully implement QbD (quality-by-design). Near-infrared (NIR) spectroscopy has been extensively applied as an in-line/on-line analytical tool in biomedical and chemical industries. In this study, the film thickness on pharmaceutical pellets was examined for quantification using in-line NIR spectroscopy during a fluid-bed coating process. A precise monitoring of coating thickness and its prediction with a suitable control strategy is crucial to the quality assurance of solid dosage forms including dissolution characteristics. Pellets of a test formulation were manufactured and coated in a fluid-bed by spraying a hydroxypropyl methylcellulose (HPMC) coating solution. NIR spectra were acquired via a fiber-optic probe during the coating process, followed by multivariate analysis utilizing partial least squares (PLS) calibration models. The actual coating thickness of pellets was measured by two separate methods, confocal laser scanning microscopy (CLSM) and laser diffraction particle size analysis (LD-PSA). Both characterization methods gave superb correlation results, and all determination coefficient (R(2)) values exceeded 0.995. In addition, a prediction coating experiment for 70min demonstrated that the end-point can be accurately designated via NIR in-line monitoring with appropriate calibration models. In conclusion, our approach combining in-line NIR monitoring with CLSM and LD-PSA can be applied as an effective PAT tool for fluid-bed pellet coating processes.     

Physico-chemical solid-state characterization of omeprazole sodium: Thermal,spectroscopic and crystallinity studies

The physical characterization of active pharmaceutical substances is crucial to the successful development of the final drug product. The different solid forms and variations in the degree of crystallinity can lead to significantly different physical and chemical properties, including color, morphology, stability, dissolution and bioavailability. In the case of omeprazole sodium (OMS), its chemical structures contain a specific number of water molecules (hydrate). The behavior of pharmaceutical hydrates has become the object of increasing attention over the past decade, primarily due to the potential impact of hydrates on the development process and dosage form performance. The present study was designed to characterize and evaluate the crystallinity of omeprazole sodium, dehydrated omeprazole sodium (DOMS) and omeprazole free base (OM) using a variety of techniques including thermal analysis (thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC)), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Furthermore, an NMR spectroscopy study was also carried out to clarify the conformation and crystal structure.