Perspectives in the use of spectroscopy to characterise pharmaceutical solids

Spectrochip-based Calibration Curve Modeling (CCM) for Rapid and Accurate Multiple Analytes Quantification in Urinalysis

Most urine test strips are intended to enable the general population to rapidly and easily diagnose potential renal disorders. It is semi-quantitative in nature, and although the procedure is straightforward, certain factors will affect the judgmental outcomes. This study describes rapid and accurate quantification of twelve urine test strip parameters: leukocytes, nitrite, urobilinogen, protein, pH, occult blood, specific gravity, ketone, bilirubin, glucose, microalbumin, and creatinine using a micro-electromechanical system (MEMS)-based spectrophotometer, known as a spectrochip. For each parameter, absorption spectra were measured three times independently at eight different concentration levels of diluted standard solutions, and the average spectral intensities were calculated to establish the calibration curve under the characteristic wavelength (λ c ). Then, regression analysis on the calibration curve was performed with GraphPad Prism software, which revealed that the coefficient of determination (R 2 ) of the modeled calibration curves was greater than 0.95. This result illustrates that the measurements exceed standard levels, confirming the importance of a spectrochip for routine multi-parameter urine analysis. Thus, it is possible to obtain the spectral signal strength for each parameter at its characteristic wavelength in order to compare directly with the calibration curves in the future, even in situations when sample concentration is unknown. Additionally, the use of large testing machines can be reduced in terms of cost, time, and space by adopting a micro urine testing platform based on spectrochip, which also improves operational convenience and effectively enables point-of-care (POC) testing in urinalysis.

Detailed accounts of segregation mechanisms and the evolution of pharmaceutical blend segregation analysis: A review

Segregation refers to the separation of components in a powder mixture, resulting in potential issues related to concentration inhomogeneity. Any well-mixed blend that undergoes secondary processing is inherently susceptible to segregation which, if unmitigated, will lead to active compound concentration variance and poorer product quality. The consequences range from adverse financial impact to manufacturers with product failures to the detrimental health effects to product users. Hence, the topic of segregation is of paramount importance to the industry, requiring it to be dissected and scrutinized intensively by scientists worldwide. This review provides a well-crafted theoretical framework designed to understand the common segregation mechanisms that manufacturing facilities face, followed by the efforts to gauge the degree of segregation. To minimize segregation in blends, various approaches - mathematical modeling, empirical experiments, and empirical methods with modeling consideration - have been utilized in segregation research and are covered in this review. The past segregation studies from many fields are discussed, with particular emphasis on pharmaceuticals. The review also discusses the evolution and advances in mixing technology and storage systems implemented by the pharmaceutical industry to prevent segregation. In the conclusion, the authors articulated their perspectives on potential mitigation measures, including suggestions for improvements and future studies.

Evaluation of the effect of granule size of raw tableting materials on critical quality attributes of tablets during the continuous tablet manufacturing process using near-infrared spectroscopy

OBJECTIVE

The effects of granule size of raw materials on tablet hardness (TH) and weight (TW) in the continuous tablet manufacturing process (CTMP) were investigated using near-infrared spectroscopy (NIRS).

METHODS

Granule materials of different sizes were prepared by extrusion granulation from a standard granule formula powder containing lactose/starch and 4.5% acetaminophen. Large-, small-, and medium-sized granules were sequentially filled in a hopper, and tablets were produced continuously using a single-shot tableting machine. After arranging approximately 500 tablets in order, the tablets were subjected to NIRS. A total of 450 NIRS datasets were divided into three groups of 150 each (calibration, validation 1, and validation 2 datasets).

RESULTS

The best fitted calibration models for predicting TH and TW were obtained, with sufficient accuracy, based on NIRS using the partial least squares regression, and comprised both physical and chemical information. The regression and loading vectors of the calibration models suggested that the models used to predict TH and TW involve physical information based on geometrical factors of the tablet and chemical information related to binder-related intermolecular interactions.

CONCLUSIONS

The changes in the predicted value profiles of TH and TW using NIRS reflected the changes in the measured values depending on the raw granule size during CTMP.

Mitigating Drug Stability Challenges Through Cocrystallization

Drug stability plays a significant role in the pharmaceutical industry from early-phase drug discovery to product registration as well as the entire life cycle of a product. Various formulation approaches have been employed to overcome drug stability issues. These approaches are sometimes time-consuming which ultimately affect the timeline of the product launch and may further require formulation optimization steps, affecting the overall cost. Pharmaceutical cocrystal is a well-established route to fine tune the biopharmaceutical properties of drugs without covalent modification. This article highlights the role of cocrystallization in mitigating the stability issues of challenging drug molecules. Representative case studies wherein the drug stability issue is addressed through pharmaceutical cocrystals have been discussed briefly and are summarized in tabular form. The emphasis has been made on the structural information of cocrystals and understanding the mechanism that improves the stability of the parent drug through cocrystallization. Besides, a guided strategy has been proposed to modulate the stability of drug molecules through cocrystallization approach. Finally, the stability concern of fixed-dose or drug combinations and the challenges associated with cocrystals are also touched.

Development of a Microgram Scale Video-Microscopic Method to Investigate Dissolution Behavior of Poorly Water-Soluble Drugs

Poor aqueous solubility is a common characteristic of new drug candidates, which leads to low or inconsistent oral bioavailability. This has sparked an interest in material efficient testing of solubility and dissolution rate. The aim was to develop a microgram scale video-microscopic method to screen the dissolution rates of poorly water-soluble drugs. This method was applied to six drugs (carvedilol, diazepam, dipyridamole, felodipine, fenofibrate, and indomethacin) in fasted state simulated intestinal fluid (FaSSIF), of indomethacin in buffer with varying pH, and of diazepam and dipyridamole in customized media. An additional aim was to track phase transformations for carbamazepine in FaSSIF. The dissolution rates and particle behavior of the drugs were investigated by tracking particle surface area over time using optical video-microscopy. Applying miniaturized UV spectroscopic dissolution resulted in a similar grouping of dissolution rates and pH effects, as for the video-microscopic setup. Using customized media showed that lysophospholipid enhanced the dissolution rate of diazepam and dipyridamole. The video-microscopic setup allowed for the nucleation of transparent particles on dissolving carbamazepine particles to be tracked over time. The developed setup offers a material efficient screening approach to group drugs according to dissolution rate, where the use of optical microscopy helps to achieve a high sample throughput.

Comparison of genuine, generic and counterfeit Cialis tablets using vibrational spectroscopy and statistical methods

The dubious online market in phosphodiesterase type 5 inhibitors is growing on a global scale. Counterfeit medical products can represent health issues for the user and cause medical mistrust. Within this work, genuine Cialis containing the active pharmaceutical ingredient (API) tadalafil, its generics available in the Czech Republic and the Cialis tablets from questionable online pharmacies were analysed. The methods of infra-red and Raman spectroscopy were used for the identification of the counterfeit tablets and for the verification of their API and excipients. All 9 tablets from online pharmacies were counterfeit with 2 of them even containing a different API (sildenafil, vardenafil). In addition, Raman mapping was used to determine the API and excipients' distribution and, in combination with multivariate data analysis, to separate similar tablets in clusters and to identify the outliers. Scanning electron microscopy of the samples revealed that the process of a wet granulation of micronized API was used during the formulation of the tablets. This comprehensive approach of analysis can be used for advanced exploration of the dubious samples of various medical products.

Application of Near-Infrared Spectroscopy to statistical control in freeze-drying processes

Batch freeze-drying of pharmaceutical products in vials may result in a high degree of intra-batch variability due to several reasons, e.g. non uniform heating rate in the drying chamber. Therefore, product quality in the final product has to be checked in a statistically significant number of samples, in particular in the stage of process development. Here, Fourier-Transform Near-Infrared Spectroscopy is proposed as a fast, non-destructive technique for an off-line Statistical Quality Control application. At first, results obtained in a batch where product features are satisfactory are used to identify a target quality threshold. Then, a statistical controller is developed in such a way that in a production run it is possible to quickly check if product quality exceeds the desired threshold or not. Two approaches based on multivariate analysis are presented: one employs the Hotelling T² and Mahalanobis statistics to calculate control charts, the other is an application of Partial Least Squares for discriminant analysis (PLS-DA). Control charts and PLS-DA were trained with samples obtained in a run where sucrose solution was processed and validated in other runs where the final product was known to have the desired qualitative characteristics or not. Overall, out-of-specification samples can be predicted by control charts and PLS-DA with 99% and 98% accuracy respectively. PLS-DA was shown to be able to better identify samples correctly processed, while the control charts where more accurate to identify vials where something went wrong. Focusing on residual moisture of the final product, all samples where it was higher than the target value were always correctly identified.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Raman and Terahertz Spectroscopic Characterization of Solid-state Cocrystal Formation within Specific Active Pharmaceutical Ingredients

Cocrystallization of specific active pharmaceutical ingredients (APIs) in the solid-state phase is becoming a feasible way to improve their corresponding physicochemical properties and ultimate bioavailability without making and breaking any covalent bonds within them. Many recent reports deal with the characterization and analysis topics of pharmaceutical APIs-based cocrystals. In this mini-review, we will focus on the recent steady-state and time-dependent spectroscopic investigation into the cocrystallization of specific APIs based on both Raman and emerging terahertz spectroscopy in pharmaceutical fields. Distinctive spectral, structural and also kinetic information of pharmaceutical APIs-based cocrystals are obtained and discussed, which would highlight the potential of vibrational spectroscopy as an attractive technique for various drug research and development during cocrystallization of specific APIs.

Prediction of drug dissolution from Toremifene 80 mg tablets by NIR spectroscopy

The aim of our study was to justify substitution of dissolution analysis for NIR measurement of Toremifene 80 mg tablets. We studied implementation of a NIRS method by integrating the method development to discrimination power of the dissolution method. Hence, we analyzed 20 DoE tablet batches and studied which of the critical formulation factors affecting dissolution were statistically significant. To study if these factors can be detected by NIRS, PLS calibration models were developed. Finally, PLS model was built to correlate NIR data with the actual dissolution results to predict the released amount of toremifene in 30 min. To obtain the data the tablet batches were measured by NIR using diffuse reflectance technique and multivariate analysis tool was used to calibrate the NIRS models. Correlations between the critical formulation factors and the NIR spectra of Toremifene 80 mg tablet were shown and it was thus justified to develop a NIRS prediction model for dissolution. Variance (R²), standard error of estimate (SEE) and standard error of prediction (SEP) of the model were 90.0%, 4.3% and 5.9%, respectively. It was thus shown that multi-phased and time consuming dissolution procedure could be substituted for fast non-invasive NIRS method.

Real-time monitoring of pharmaceutical properties of medical tablets during direct tableting process by hybrid tableting process parameter-time profiles

BACKGROUND

Real-time monitoring is required for the pharmaceutical manufacturing process to produce high-quality pharmaceutical products.

OBJECTIVE

Changes in the critical tableting process parameters of single-punch tableting machine due to variability in the moisture content of the raw powders were monitored by hybrid tableting pressure-time profiles.

METHODS

After mixing of the raw powders, which consisted of theophylline, anhydrous lactose, potato starch and crystalline cellulose, they were stored at 0%, 45%, or 75% relative humidity (RH) for 24 h, respectively. Continuous tablet productions were carried out using the mixed powder samples at 10%, 45%, or 75% RH, respectively. The critical process parameters, such as upper and lower puncture pressures, die wall pressures, and inter-punch distances were recoded with the tableting machine, and then, tablet hardness (H), weight (W) and disintegration time (DT) of the tablets were measured.

RESULTS

Hybrid tableting pressure-time profiles were obtained from various critical process parameters, and calibration models to predict pharmaceutical properties were calculated based on the hybrid profiles using a partial-least-squares regression (PLSR) method. In addition, the consistency of the calibration models were verified by constructing robust calibration models.

CONCLUSION

Informetrical analysis for tablets based on hybrid tableting pressure-time profiles could evaluate the change of tablet properties dependent on the moisture content in the raw powders during the tableting process. The changes of tableting properties and elasticity were caused by agglomeration of powder particles at moisture content.

Homogeneity of amorphous solid dispersions - an example with KinetiSol®

KinetiSol^® is a high-shear, fusion-based technology capable of producing stable amorphous solid dispersions (ASDs) without the assistance of solvent. KinetiSol^® has proven successful with multiple challenging BCS class II and IV drugs, where drug properties like thermal instability or lack of appreciable solubility in volatile solvents make hot melt extrusion or spray drying unfeasible. However, there is a necessity to characterize the ASDs like those made by the KinetiSol^® process, in order to better understand whether KinetiSol^® is capable of homogeneously dispersing drug throughout a carrier in a short (<40 s) processing time. Our study utilized the high melting point, BCS class II drug, meloxicam, in order to evaluate the degree of homogeneity of 1, 5, and 10% w/w KinetiSol^®-processed samples. Powder blend homogeneity and content uniformity were evaluated, and all samples demonstrated a meloxicam concentration % relative standard deviation of ≤2.0%. SEM/EDS was utilized to map elemental distribution of the processed samples, which confirmed KinetiSol^®-processed materials were homogeneous at a 25 µm² area. Utilizing Raman spectroscopy, we were able to verify the amorphous content of the processed samples. Finally, we utilized ssNMR ¹H spin-lattice relaxation measurement to evaluate the molecular miscibility of meloxicam with the polymer at 1% w/w drug load, for the first time, and determined the processed sample was highly miscible at ∼200 nm scale. In conclusion, we determined the KinetiSol^® process is capable of producing ASDs that are homogeneously and molecularly well-dispersed drug-in-polymer at drug concentrations as low as 1% w/w.

Time-Gated Raman Spectroscopy for Quantitative Determination of Solid-State Forms of Fluorescent Pharmaceuticals

Raman spectroscopy is widely used for quantitative pharmaceutical analysis, but a common obstacle to its use is sample fluorescence masking the Raman signal. Time-gating provides an instrument-based method for rejecting fluorescence through temporal resolution of the spectral signal and allows Raman spectra of fluorescent materials to be obtained. An additional practical advantage is that analysis is possible in ambient lighting. This study assesses the efficacy of time-gated Raman spectroscopy for the quantitative measurement of fluorescent pharmaceuticals. Time-gated Raman spectroscopy with a 128 × (2) × 4 CMOS SPAD detector was applied for quantitative analysis of ternary mixtures of solid-state forms of the model drug, piroxicam (PRX). Partial least-squares (PLS) regression allowed quantification, with Raman-active time domain selection (based on visual inspection) improving performance. Model performance was further improved by using kernel-based regularized least-squares (RLS) regression with greedy feature selection in which the data use in both the Raman shift and time dimensions was statistically optimized. Overall, time-gated Raman spectroscopy, especially with optimized data analysis in both the spectral and time dimensions, shows potential for sensitive and relatively routine quantitative analysis of photoluminescent pharmaceuticals during drug development and manufacturing.

Amorphization of thiamine chloride hydrochloride: A study of the crystallization inhibitor properties of different polymers in thiamine chloride hydrochloride amorphous solid dispersions

Amorphous solid dispersions of thiamine chloride hydrochloride (THCl) were created using a variety of polymers with different physicochemical properties in order to investigate how effective the various polymers were as THCl crystallization inhibitors. THCl:polymer dispersions were prepared by lyophilizing solutions of THCl and amorphous polymers (guar gum, pectin, κ-carrageenan, gelatin, and polyvinylpyrrolidone (PVP)). These dispersions were stored at select temperature (25 and 40°C) and relative humidity (0, 23, 32, 54, 75, and 85% RH) conditions and monitored at different time points using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Moisture sorption isotherms of all samples were also obtained. Initially amorphous THCl was produced in the presence of ≥40% w/w pectin, κ-carrageenan, gelatin, and guar gum or ≥60% w/w PVP. Trends in polymer THCl crystallization inhibition (pectin≥κ-carrageenan>gelatin>guar gum≫PVP) were primarily based on the ability of the polymer to interact with THCl via hydrogen bonding and/or ionic interactions. The onset of THCl crystallization from the amorphous dispersions was also related to storage conditions. THCl remained amorphous at low RH conditions (0 and 23% RH) in all 1:1 dispersions except THCl:PVP. THCl crystallized in some dispersions below the glass transition temperature (T_g) but remained amorphous in others at T~T_g. At high RHs (75 and 85% RH), THCl crystallized within one day in all samples. Given the ease of THCl amorphization in the presence of a variety of polymers, even at higher vitamin concentrations than would be found in foods, it is likely that THCl is amorphous in many low moisture foods.

Investigation of the Sensitivity of Transmission Raman Spectroscopy for Polymorph Detection in Pharmaceutical Tablets

Polymorph detection is critical for ensuring pharmaceutical product quality in drug substances exhibiting polymorphism. Conventional analytical techniques such as X-ray powder diffraction and solid-state nuclear magnetic resonance are utilized primarily for characterizing the presence and identity of specific polymorphs in a sample. These techniques have encountered challenges in analyzing the constitution of polymorphs in the presence of other components commonly found in pharmaceutical dosage forms. Laborious sample preparation procedures are usually required to achieve satisfactory data interpretability. There is a need for alternative techniques capable of probing pharmaceutical dosage forms rapidly and nondestructively, which is dictated by the practical requirements of applications such as quality monitoring on production lines or when quantifying product shelf lifetime. The sensitivity of transmission Raman spectroscopy for detecting polymorphs in final tablet cores was investigated in this work. Carbamazepine was chosen as a model drug, polymorph form III is the commercial form, whereas form I is an undesired polymorph that requires effective detection. The concentration of form I in a direct compression tablet formulation containing 20% w/w of carbamazepine, 74.00% w/w of fillers (mannitol and microcrystalline cellulose), and 6% w/w of croscarmellose sodium, silicon dioxide, and magnesium stearate was estimated using transmission Raman spectroscopy. Quantitative models were generated and optimized using multivariate regression and data preprocessing. Prediction uncertainty was estimated for each validation sample by accounting for all the main variables contributing to the prediction. Multivariate detection limits were calculated based on statistical hypothesis testing. The transmission Raman spectroscopic model had an absolute prediction error of 0.241% w/w for the independent validation set. The method detection limit was estimated at 1.31% w/w. The results demonstrated that transmission Raman spectroscopy is a sensitive tool for polymorphs detection in pharmaceutical tablets.

Chemometrics-assisted solid-state characterization of pharmaceutically relevant materials. Polymorphic substances

Current regulations command to properly characterize pharmaceutically relevant solid systems. Chemometrics comprise a range of valuable tools, suitable to process large amounts of data and extract valuable information hidden in their structure. This review aims to detail the results of the fruitful association between analytical techniques and chemometrics methods, focusing on those which help to gain insight into the characteristics of drug polymorphism as an important aspect of the solid state of bulk drugs and drug products. Hence, the combination of Raman, terahertz, mid- and near- infrared spectroscopies, as well as instrumental signals resulting from X-ray powder diffraction, ¹³C solid state nuclear magnetic resonance spectroscopy and thermal methods with quali-and quantitative chemometrics methodologies are examined. The main issues reviewed, concerning pharmaceutical drug polymorphism, include the use of chemometrics-based approaches to perform polymorph classification and assignment of polymorphic identity, as well as the determination of given polymorphs in simple mixtures and complex systems. Aspects such as the solvation/desolvation of solids, phase transformation, crystallinity and the recrystallization from the amorphous state are also discussed. A brief perspective of the field for the next future is provided, based on the developments of the last decade and the current state of the art of analytical instrumentation and chemometrics methodologies.

Is it possible to find presence of lactose in pharmaceuticals? - Preliminary studies by ATR-FTIR spectroscopy and chemometrics

Lactose and saccharose have the same molecular formula; however, the arrangement of their atoms is different. A major difference between lactose and saccharose with regard to digestion and processing is that it is not uncommon for individuals to be lactose intolerant (around two thirds of the population has a limited ability to digest lactose after infancy), but it is rather unlikely to be saccharose intolerant. The pharmaceutical industry uses lactose and saccharose as inactive ingredients of drugs to help form tablets because of their excellent compressibility properties. Some patients with severe lactose intolerance may experience symptoms of many allergic reactions after taking medicine that contains this substance. People who are specifically "allergic" to lactose (not just lactose intolerant) should not use tablets containing this ingredient. Fourier Transform Infrared (FTIR) spectroscopy has a unique chemical fingerprinting capability and plays a significant important role in the identification and characterization of analyzed samples and hence has been widely used in pharmaceutical science. However, a typical FTIR spectrum collected from tablets contains a myriad of valuable information hidden in a family of tiny peaks. Powerful multivariate spectral data processing can transform FTIR spectroscopy into an ideal tool for high volume, rapid screening and characterization of even minor tablet components. In this paper a method for distinction between FTIR spectra collected for tablets with or without lactose is presented. The results seem to indicate that the success of identifying one component in FTIR spectra collected for pharmaceutical composition (that is tablet) is largely dependent on the choice of the chemometric technique applied.

Recent Advances in Solid-State Analysis of Pharmaceuticals

Current analytical techniques for characterizing solid-state pharmaceuticals include powder x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, infrared spectroscopy, Raman spectroscopy, electron microscopy and nuclear magnetic resonance. Powder x-ray diffraction and differential scanning calorimetry are mainstream techniques but they lack spatial resolution. Scanning electron microscopy and micro-Raman spectroscopy provide good chemical and optical characterization but they are not capable of analysing very small nanoparticles. Transmission electron microscopy and nano-thermal analysis can provide explicit characterization of nanoparticles but they are invasive. Nuclear magnetic resonance offers good spatial resolution but its use is mainly limited by poor sensitivity and high costs. In view of the many challenges posed by existing methods, new and novel techniques are being continually researched and developed to cater to the growing number of solid formulations in the pipeline and in the market. Some of the recent advances attained in the solid-state analysis of pharmaceutical are summarized in this review article.

Assessment of active pharmaceutical ingredient particle size in tablets by Raman chemical imaging validated using polystyrene microsphere size standards

Particle size is a critical parameter for controlling pharmaceutical quality. The aim of this study was to assess the size of the micrometer-scale active pharmaceutical ingredients (API) in tablets using Raman chemical imaging and to understand the effects of formulation on particle size. Model tablets containing National Institute of Standards and Technology traceable polystyrene microsphere size standards were developed to determine the binarization threshold value of Raman chemical images for API particle sizing in specific formulations and processes. Three sets of model tablets containing 5, 10, and 15 μm polystyrene microspheres, used to mimic API, were prepared using a commercial tablet formulation (Ebastel tablets, mean API particle size was about 5 μm). Raman mapping with a 50× objective (NA, 0.75) was applied to tablet cross-sections, and particle size of polystyrene microspheres was estimated from binary images using several binarization thresholds. Mean particle size for three sets of polystyrene microspheres showed good agreement between pre- and postformulation (the slope = 1.024, R = 1.000) at the specific threshold value ((mean + 0.5σ) of the polystyrene-specific peak intensity histogram), regardless of particle agglomeration, tablet surface roughness, and laser penetration depth. The binarization threshold value showed good applicability to Ebastel tablets, where the API-specific peak intensity histogram showed a pattern similar to that of polystyrene microspheres in model tablets. The model tablets enabled determination of an appropriate binarization threshold for assessing the mean particle size of micrometer-scale API in tablets by utilizing the unique physicochemical properties of polystyrene microspheres.

Computational Raman spectroscopy of organometallic reaction products in lithium and sodium-based battery systems

We demonstrate that small molecular dimers of Li/Na organometallic compounds can provide relevant information about the inter- and intramolecular interactions of their respective crystallographic configurations, which in turn leads to an improved description of their respective Raman spectra.

Polymorph screening of an active material

Polymorph screening is currently one of the most important tasks for innovators and for generic companies from both pharmaceutical and intellectual property rights aspects. The different polymorphs have different physicochemical properties, such as the crystal polymorph-dependent solubility which influences the bioavailability. A former drug candidate obtained from Sanofi Pharmaceutical Company (Hungary) was investigated to explore its polymorphism, to distinguish the morphologies generated by analytical examinations and to investigate their relative stabilities. An Avantium Crystal 16 automatic laboratory reactor system was used for the polymorph studies and the studies of their dissolution. Eight polymorphs were obtained by crystallization and transformation methods then characterized by XRPD, DSC, and Raman spectroscopy, scanning electron microscopy, and light microscopy. All the morphologies could be stored in solid without any form transformation for a long time (2 years investigated). According to the first relative stability results, Form I, III, IVa, V, VI, VII are unambiguously metastable forms. Form II and IVb have similar thermodynamic stabilities, that were higher than those of the other polymorphs. A special dissolution medium was developed in which the eight polymorphs showed clear differences in the rate of dissolution.

Terahertz pulsed imaging as an advanced characterisation tool for film coatings--a review

Solid dosage forms are the pharmaceutical drug delivery systems of choice for oral drug delivery. These solid dosage forms are often coated to modify the physico-chemical properties of the active pharmaceutical ingredients (APIs), in particular to alter release kinetics. Since the product performance of coated dosage forms is a function of their critical coating attributes, including coating thickness, uniformity, and density, more advanced quality control techniques than weight gain are required. A recently introduced non-destructive method to quantitatively characterise coating quality is terahertz pulsed imaging (TPI). The ability of terahertz radiation to penetrate many pharmaceutical materials enables structural features of coated solid dosage forms to be probed at depth, which is not readily achievable with other established imaging techniques, e.g. near-infrared (NIR) and Raman spectroscopy. In this review TPI is introduced and various applications of the technique in pharmaceutical coating analysis are discussed. These include evaluation of coating thickness, uniformity, surface morphology, density, defects and buried structures as well as correlation between TPI measurements and drug release performance, coating process monitoring and scale up. Furthermore, challenges and limitations of the technique are discussed.

In-line monitoring of the drug content of powder mixtures and tablets by near-infrared spectroscopy during the continuous direct compression tableting process

Continuous manufacturing methods offer economic and quality advantages when compared with batch manufacturing methods. In continuous manufacturing, one requires real time assurance of quality of product via the implementation of PAT tools. This study focuses on an in-line near-infrared (NIR) spectroscopic method for determining the drug content of powder mixtures and tablets during a continuous tableting process. Tablets consisting of acetaminophen (20-30%), lactose (69.07-78.93%) and magnesium stearate (0.93-1.07%) were prepared in a continuous direct compression line that consisted of two loss-in-weight feeders, one for acetaminophen and one for premixed lactose and magnesium stearate, and a continuous mixer followed by a rotary tablet press. NIR spectroscopy was applied to the continuous mixer and tablet press to perform a 100% product check at full tableting speed. The UV-spectrophotometric method was used as an off-line reference method to determine the acetaminophen content in the samples. The powder mixture and tablet samples were taken during the process for the calibration of continuous mixer and tablet press, respectively. For the continuous mixer, model creation with the PLS method yielded R-Square and RMSEC (root mean square error of calibration) values of 0.975% and 0.56%, respectively. For the tablet press, the corresponding R-Square and RMSEC values were 0.943% and 0.75%, respectively. A test run demonstrated good predictability in the estimation of the API content in the powder mixtures and tablets during the continuous tableting process. For the continuous mixer and tablet press, the RMSEP (root mean square error of prediction) values were 0.96% and 1.37%, respectively. This study demonstrates that an NIR instrument capable of fast spectra acquisition can be a valuable tool for the in-line monitoring of the continuous mixing and tableting processes.

Structural elucidation of rapid solution-mediated phase transitions in pharmaceutical solids using in situ synchrotron SAXS/WAXS

In situ elucidation of kinetics of solution-mediated phase transformations using direct structural determination has been achieved using synchrotron SAXS/WAXS radiation. Using theophylline as a model drug with known phase transformation from anhydrate to monohydrate form in aqueous conditions within a few minutes, the kinetics of the structural transition were resolved at the second scale, and the results achieved agreed well with those determined using indirect approaches such as Raman spectroscopy. The recrystallization of the monohydrate in situ (due to its lower solubility) from dissolved anhydrate solution (higher solubility) is demonstrated directly, highlighting a major issue for such compounds in application. The technique has the additional benefit of having the potential to identify intermediate structures which are not readily achievable with in situ spectroscopic techniques, as well as being amenable to high throughput approaches.

Spectroscopic properties of neuroleptics: IR and Raman spectra of Risperidone (Risperdal) and of its mono- and di-protonated forms

Structures and IR and Raman spectra of Risperidone in its neutral, mono- and di-protonated forms were calculated in gas phase by DFT-B3LYP/6-31G* level. Mono-protonation occurs at the nitrogen atom of the piperidine ring, while nitrogen atom of the pyrimidine ring is the preferred site for the second protonation. The lowest-energy structure of the mono-protonated Risperidone is characterized by formation of a strong seven-membered O(pyrimidine ring)⋯(+)H-N(piperidine ring) intramolecular hydrogen-bonded cycle. In the high-energy spectral region (3500-2500 cm(-1)), the bands of the N-H(+) stretches and the changes in wavenumbers and IR intensities of the C-H stretches near to the piperidine nitrogen atom (Bohlmann effect) are potentially useful to discriminate conformations and protonation states. Di-protonated structures can be identified by the presence of an isolated absorption peak located in the low-energy IR region (660-690 cm(-1)), attributed to the out-of-plane N-H(+)(pyrimidine ring) bending deformation. The most intense Raman band of neutral Risperidone placed at ca. 1500 cm(-1), assigned to C=C(pyrimidine ring) stretch + C=N(pyrimidine ring) stretch, can be a useful vibrational marker to distinguish the neutral from the protonated forms.

In-line prediction of drug release profiles for pH-sensitive coated pellets

A new method for the prediction of the drug release profiles during a running pellet coating process from in-line near infrared (NIR) measurements has been developed. The NIR spectra were acquired during a manufacturing process through an immersion probe. These spectra reflect the coating thickness that is inherently connected with the drug release. Pellets sampled at nine process time points from thirteen designed laboratory-scale coating batches were subjected to the dissolution testing. In the case of the pH-sensitive Acryl-EZE coating the drug release kinetics for the acidic medium has a sigmoid form with a pronounced induction period that tends to grow along with the coating thickness. In this work the autocatalytic model adopted from the chemical kinetics has been successfully applied to describe the drug release. A generalized interpretation of the kinetic constants in terms of the process and product parameters has been suggested. A combination of the kinetic model with the multivariate Partial Least Squares (PLS) regression enabled prediction of the release profiles from the process NIR data. The method can be used to monitor the final pellet quality in the course of a coating process.