Quantification of swelling and erosion in the controlled release of a poorly water-soluble drug using synchrotron X-ray computed microtomography

Exploring the Effectiveness of Carboxymethylated and Crosslinked Albizia Procera Gum in Diltiazem Hydrochloride Matrix Tablets: A Comparative Analysis

This study investigates the efficacy of modified Albizia procera gum as a release-retardant polymer in Diltiazem hydrochloride (DIL) matrix tablets. Carboxymethylated Albizia procera gum (CAP) and ionically crosslinked carboxymethylated Albizia procera gum (Ca-CAP) were utilized, with Ca-CAP synthesized via crosslinking CAP with calcium ions (Ca2+) using calcium chloride (CaCl2). FTIR analysis affirmed polymer compatibility, while Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) assessed thermal behavior and crystallinity, respectively. Zeta potential analysis explored surface charge and electrostatic interactions, while rheology examined flow and viscoelastic properties. Swelling and erosion kinetics provided insights into water penetration and stability. CAP's carboxymethyl groups (-CH2-COO-) heightened divalent cation reactivity, and crosslinking with CaCl2 produced Ca-CAP through -CH2-COO- and Ca2+ interactions. Structural similarities between the polymers were revealed by FTIR, with slight differences. DSC indicated modified thermal behavior in Ca-CAP, while Zeta potential analysis showcased negative charges, with Ca-CAP exhibiting lower negativity. XRD highlighted increased crystallinity in Ca-CAP due to calcium crosslinking. Minimal impact on RBC properties was observed with both polymers compared to the positive control as water for injection (WFI). Ca-CAP exhibited improved viscosity, strength, controlled swelling, and erosion, allowing prolonged drug release compared to CAP. Stability studies confirmed consistent six-month drug release, emphasizing Ca-CAP's potential as a stable, sustained drug delivery system over CAP. Robustness and accelerated stability tests supported these findings, underscoring the promise of Ca-CAP in controlled drug release applications.

The Effect of Polymer-Solvent Interaction on the Swelling of Polymer Matrix Tablets: A Magnetic Resonance Microscopy Study Complemented by Bond Fluctuation Model Simulations

Polymer matrix tablets are an important drug-delivery system widely used for oral drug administration. Understanding the tablet hydration process, both experimentally and theoretically, is, thus, very important for the development of drug delivery systems that exhibit high drug loading capacity and controlled release potential. In this study, we used magnetic resonance microscopy (MRM) to nondestructively and dynamically analyze the water hydration process of xanthan-based tablets. The swelling process was characterized by well-resolved fronts of erosion, swelling, and penetration. The experimental results were complemented by numerical simulations of the polymer matrix hydration process. In the simulations, the polymer tablet matrix was modeled as an assembly of interacting chains with embedded drug particles, while its hydration process was mediated by interaction with solvent particles. The swelling dynamics were modeled within a Monte Carlo-based bond fluctuation model (BFM) that elegantly accounted for steric and nearest-neighbor interactions. This study provides an efficient experimental-theoretical approach for the study of polymer matrix swelling processes.

Microstructure Formation and Characterization of Long-Acting Injectable Microspheres: The Gateway to Fully Controlled Drug Release Pattern

Long-acting injectable microspheres have been on the market for more than three decades, but if calculated on the brand name, only 12 products have been approved by the FDA due to numerous challenges in achieving a fully controllable drug release pattern. Recently, more and more researches on the critical factors that determine the release kinetics of microspheres shifted from evaluating the typical physicochemical properties to exploring the microstructure. The microstructure of microspheres mainly includes the spatial distribution and the dispersed state of drug, PLGA and pores, which has been considered as one of the most important characteristics of microspheres, especially when comparative characterization of the microstructure (Q3) has been recommended by the FDA for the bioequivalence assessment. This review extracted the main variables affecting the microstructure formation from microsphere formulation compositions and preparation processes and highlighted the latest advances in microstructure characterization techniques. The further understanding of the microsphere microstructure has significant reference value for the development of long-acting injectable microspheres, particularly for the development of the generic microspheres.

Advances in Structure Pharmaceutics from Discovery to Evaluation and Design

Drug delivery systems (DDSs) play an important role in delivering active pharmaceutical ingredients (APIs) to targeted sites with a predesigned release pattern. The chemical and biological properties of APIs and excipients have been extensively studied for their contribution to DDS quality and effectiveness; however, the structural characteristics of DDSs have not been adequately explored. Structure pharmaceutics involves the study of the structure of DDSs, especially the three-dimensional (3D) structures, and its interaction with the physiological and pathological structure of organisms, possibly influencing their release kinetics and targeting abilities. A systematic overview of the structures of a variety of dosage forms, such as tablets, granules, pellets, microspheres, powders, and nanoparticles, is presented. Moreover, the influence of structures on the release and targeting capability of DDSs has also been discussed, especially the in vitro and in vivo release correlation and the structure-based organ- and tumor-targeting capabilities of particles with different structures. Additionally, an in-depth discussion is provided regarding the application of structural strategies in the DDSs design and evaluation. Furthermore, some of the most frequently used characterization techniques in structure pharmaceutics are briefly described along with their potential future applications.

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.

Development of Flow-Through Cell Dissolution Method for In Situ Visualization of Dissolution Processes in Solid Dosage Forms Using X-ray μCT

Visualization of the dynamic behavior of pharmaceutical dosage forms during the dissolution process offers a better understanding of the drug release mechanism, enabling the design of customized dosage forms. In this study, an X-ray tomography-based approach is proposed to monitor and analyze the dynamics of the structure at the pore scale level during the dissolution process. A flow-through cell dissolution apparatus was developed, capable of mimicking the standard in vitro dissolution process, which can be easily positioned in an X-ray tomography setup. The method was utilized to study the dissolution of a Capa^® (polycaprolactone)-based sustained-release 3D printed tablet. The impact of the flow rate on the active pharmaceutical ingredient (API) release rate was studied and 16 mL/min was selected as a suitable flow rate. Furthermore, cesium chloride (CsCl) was used as a contrast agent to increase the contrast between the sample and the dissolution medium. Data obtained with this novel technique were in a good agreement with the released drug rate acquired by the standard in vitro dissolution test (the similarity factor (f2) = 77%). Finally, the proposed approach allowed visualizing the internal structure of the sample, as well as real-time tracking of solution ingress into the product.

New Insight into the Impact of Effervescence on Gel Layer Microstructure and Drug Release of Effervescent Matrices Using Combined Mechanical and Imaging Characterisation Techniques

Gel layer characteristics play a crucial role in hydrophilic hydroxypropyl methylcellulose (HPMC) matrix development. Effervescent agents have the potential to affect the gel layer microstructures. This study aimed to investigate the influence of effervescence on the microstructure of the gel layer around HPMC matrices using a combination of texture analysis and imaging techniques. The relationship with drug release profile and release mechanisms were also examined. The high amounts of effervescent agents promoted a rapid carbonation reaction, resulting in a high gel layer formation with a low gel strength through texture analysis. This finding was ascribed to the enhanced surface roughness and porosity observed under digital microscopy and microporous structure of the gel layer under scanning electron microscopy. The reconstructed three-dimensional images from synchrotron radiation X-ray tomographic microscopy notably exhibited the interconnected pores of various sizes from the carbonation reaction of effervescent and microporous networks, indicating the gel layer on the tablet surface. Notably, effervescence promoted the increase in interconnected porosities, which directly influenced the strength of the gel layer microstructure, drug release patterns and release mechanism of the effervescent matrix tablet. Therefore, combined mechanical characterisation and imaging techniques can provide new insights into the role of effervescent agents on the gel layer microstructure, and describe the relationship of drug release patterns and release mechanism of matrix tablets.

Visualizing fluid transport inside orally disintegrating tablets and changes in tablets using real-time X-ray radiography and X-ray computed tomography

OBJECTIVE

To investigate the disintegration of wet- and dry-compressed orally disintegrating (OD) tablets, with synchrotron radiation as the X-ray source.

SIGNIFICANCE

Pharmaceutical tablets are vital for treatment of various diseases. Therefore, they are constantly developed to ensure desirable characteristics. In particular, OD tablets need to disintegrate immediately after absorbing saliva. How these tablets absorb saliva is key to enhancing rapid product development. Recently, absorption processes have been investigated using various non-invasive techniques, including X-ray radiography and X-ray computed tomography. However, X-ray radiography studies on how water without a contrast agent is absorbed, moves, and causes a tablet to swell are scarce. Use of a contrast agent is associated with some shortcomings, including complex data analysis in some instances, alterations in the viscosity of water, and potential influence on fluid transport inside the tablet, thus possibly affecting the disintegration process.

METHODS

Real-time X-ray radiography was used to monitor the disintegration of various tablets, while X-ray computed tomography and software were used to create 3D images.

RESULTS

We demonstrated how pure water penetrated the wet-compressed tablet faster than inside the dry-compressed tablet, and how the latter swelled more. X-ray computed tomography showed the presence of voids in the tablets following water absorption.

CONCLUSION

Our methods are promising for non-destructive fluid absorption and transport investigations inside OD tablets.

Redefinition to bilayer osmotic pump tablets as subterranean river system within mini-earth via three-dimensional structure mechanism

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-μCT). In situ formed 3D structures at different in vitro drug release states were characterized comprehensively. A distinct movement pattern of NaCl crystals from the push layer to the drug layer was observed, beneath the semi-permeable coating in the desiccated tablet samples. The 3D structures at different dissolution time revealed that the pushing upsurge in the bilayer osmotic pump tablet was directed via peripheral "roadways". Typically, different regions of the osmotic front, infiltration region, and dormant region were classified in the push layer during the dissolution of drug from tablet samples. According to the observed 3D microstructures, a "subterranean river model" for the drug release mechanism has been defined to explain the drug release mechanism.

An Integrative QbD Approach for the Development and Optimization of Controlled Release Compressed Coated Formulation of Water-Soluble Drugs

Controlled release dosage forms maintain regulated pharmacokinetic profile of drug substance within its therapeutic window by ensuring constant plasma concentrations. Controlled release formulations not only increase the therapeutic efficacy of drug substances but also reduce their dose-related side effects. Present investigation was conducted to develop, optimize, and validate compressed coated controlled release tablet formulation for highly water-soluble drug substances which have no rate-controlling factor towards its release from dosage form. Drug dispersed waxy core tablet, press coated within the swellable hydrophilic polymeric barrier layer, was developed and optimized via quality by design approach (QbD) using Box-Behnken design. The optimized formulation was characterized and validated using in vitro quality control parameters. Attributes identified under SUPAC guidelines, such as drug release rates at 30 min, 6 h, and 12 h, were considered as the critical quality attributes (CQAs) that significantly affected efficiency of the compressed coated controlled release tablets. CQAs screened using risk assessment and Pareto chart analyses were used for optimizing controlled release dosage form. Findings revealed that tablets containing drug to wax ratio of 1:1, hydrophilic swellable polymer concentration of 200 mg, and prepared using compression pressure of 6.5 kg/cm² exhibited the highest desirability indices in terms of controlling the release rate of drug substance. Optimized formulation was also evaluated for swelling rate, erosion rate, and other post-compression parameters, including release kinetics. Fickian diffusion-based zero-order controlled release of BCS class I drug substance was achieved through the developed dosage form.

Mechanistic understanding of the performance of personalized 3D-printed cardiovascular polypills: A case study of patient-centered therapy

The 3D printing has become important in drug development for patient-centric therapy by combining multiple drugs with different release characteristics in a single polypill. This study explores the critical formulation and geometric variables for tailoring the release of Atorvastatin and Metoprolol as model drugs in a polypill when manufactured via pressure-assisted-microextrusion 3D printing technology. The effects of these variables on the extrudability of printing materials, drug release and other quality characteristics of polypills were studied employing a definitive screening design. The extrudability of printing materials was evaluated in terms of flow pressure, non-recoverable strain, compression rate, and elastic/plastic flow. The extrudability results helped in defining an operating space free of printing defects. The Atorvastatin compartment of polypill consisted of mesh-shaped layers while Metoprolol compartment consisted of a core surrounded by a release controlling shell with a hydrophobic septum between the two compartments. The results indicated that both the formulation and geometric variables govern the drug release of the polypill. Specifically, the use of HPMC E3 matrix, and a 2 mm distance between the strands at a weaving angle of 90° were critical in achieving the desired immediate-release profile of Atorvastatin. The core and shell design primarily determined the desired extended-release profile of Metoprolol. The carbopol and HPMC K100 concentration of 1% in the core and 10% in the shell and the number of shell layers in Metoprolol compartment were critical for achieving the desired Metoprolol dissolution. Polymer and Metoprolol content of the shell and shell-thickness affected the mechanical strength of the polypills. In conclusion, the 3D printing provides the flexibility for independently tailoring the release of different drugs in the same dosage form for patient centric therapy, and both the formulation and geometric parameters need to be optimized to achieve desired drug release.

Bridging the structure gap between pellets in artificial dissolution media and in gastro-intestinal tract in rats

Changes in structure of oral solid dosage forms (OSDF) elementally determine the drug release and its therapeutic effects. In this research, synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3D structure of enteric coated pellets recovered from the gastrointestinal tract of rats. The structures of pellets in solid state and in vitro compendium media were measured. Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media. Thus, optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media. The sphericity, pellet volume, pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for 2 h were recorded 0.47, 1.55 × 10⁸ μm³, 0.44 × 10⁸ μm³ and 27.6%, respectively. After adding pepsin and glass microspheres, the above parameters in vitro reached to 0.44, 1.64 × 10⁸ μm³, 0.38 × 10⁸ μm³ and 23.0%, respectively. Omeprazole magnesium pellets behaved similarly. The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3D structures to ensure better design, characterization and quality control of advanced OSDF.

A review of emerging technologies enabling improved solid oral dosage form manufacturing and processing

Tablets are the most widely utilized solid oral dosage forms because of the advantages of self-administration, stability, ease of handling, transportation, and good patient compliance. Over time, extensive advances have been made in tableting technology. This review aims to provide an insight about the advances in tablet excipients, manufacturing, analytical techniques and deployment of Quality by Design (QbD). Various excipients offering novel functionalities such as solubility enhancement, super-disintegration, taste masking and drug release modifications have been developed. Furthermore, co-processed multifunctional ready-to-use excipients, particularly for tablet dosage forms, have benefitted manufacturing with shorter processing times. Advances in granulation methods, including moist, thermal adhesion, steam, melt, freeze, foam, reverse wet and pneumatic dry granulation, have been proposed to improve product and process performance. Furthermore, methods for particle engineering including hot melt extrusion, extrusion-spheronization, injection molding, spray drying / congealing, co-precipitation and nanotechnology-based approaches have been employed to produce robust tablet formulations. A wide range of tableting technologies including rapidly disintegrating, matrix, tablet-in-tablet, tablet-in-capsule, multilayer tablets and multiparticulate systems have been developed to achieve customized formulation performance. In addition to conventional invasive characterization methods, novel techniques based on laser, tomography, fluorescence, spectroscopy and acoustic approaches have been developed to assess the physical-mechanical attributes of tablet formulations in a non- or minimally invasive manner. Conventional UV-Visible spectroscopy method has been improved (e.g. fiber-optic probes and UV imaging-based approaches) to efficiently record the dissolution profile of tablet formulations. Numerous modifications in tableting presses have also been made to aid machine product changeover, cleaning, and enhance efficiency and productivity. Various process analytical technologies have been employed to track the formulation properties and critical process parameters. These advances will contribute to a strategy for robust tablet dosage forms with excellent performance attributes.

Hydration Patterns in Sodium Alginate Polymeric Matrix Tablets-The Result of Drug Substance Incorporation

The purpose was to show, using destructive/nondestructive methods, that the interplay between water, tablet structure, and composition determine the unique spatiotemporal hydration pattern of polymer-based matrices. The tablets containing a 1:1 w/w mixture of sodium alginate with salicylic acid (ALG/SA) or sodium salicylate (ALG/SNA) were studied using Karl Fischer titration, differential scanning calorimetry, X-ray microtomography, and magnetic resonance imaging. As the principal results, matrix specific features were detected, e.g., "locking" of the internal part of the matrix (ALG/SA); existence of lamellar region associated with detection of free/freezing water (ALG/SA); existence of water penetrating the matrix forming specific region preceding infiltration layer (ALG/SNA); switch in the onset temperature of endothermic water peak associated with an increase in the fraction of non-freezing water weight per dry matrix weight in the infiltration layer (ALG/SNA). The existence of complicated spatiotemporal hydration patterns influenced by matrix composition and molecular properties of constituents has been demonstrated.

Polymeric Composite Matrix with High Biobased Content as Pharmaceutically Relevant Molecular Encapsulation and Release Platform

Drug delivery systems (DDS) that can temporally control the rate and extent of release of therapeutically active molecules find applications in many clinical settings, ranging from infection control to cancer therapy. With an aim to design a locally implantable, controlled-release DDS, we demonstrated the feasibility of using cellulose nanocrystal (CNC)-reinforced poly (l-lactic acid) (PLA) composite beads. The performance of the platform was evaluated using doxorubicin (DOX) as a model drug for applications in triple-negative breast cancer. A facile, nonsolvent-induced phase separation (NIPS) method was adopted to form composite beads. We observed that CNC loading within these beads played a critical role in the mechanical stability, porosity, water uptake, diffusion, release, and pharmacological activity of the drug from the delivery system. When loaded with DOX, composite beads significantly controlled the release of the drug in a pH-dependent pattern. For example, PLA/CNC beads containing 37.5 wt % of CNCs showed a biphasic release of DOX, where 41 and 82% of the loaded drug were released at pH 7.4 and pH 5.5, respectively, over 7 days. Drug release followed Korsmeyer's kinetics, indicating that the release mechanism was mostly diffusion and swelling-controlled. We showed that DOX released from drug-loaded PLA/CNC composite beads locally suppressed the growth and proliferation of triple-negative breast cancer cells, MBA-MB-231, via the apoptotic pathway. The efficacy of the DDS was evaluated in human tissue explants. We envision that such systems will find applications for designing biobased platforms with programmed stability and drug delivery functions.

DoE-Based Design of a Simple but Efficient Preparation Method for a Non-Effervescent Gastro-Retentive Floating Tablet Containing Metformin HCl

A sustained-release non-effervescent floating matrix tablet was prepared using a simple and efficient direct compression of spray-dried granules containing metformin hydrochloride and cetyl alcohol with hydroxypropyl methylcellulose K15M (HPMC K15M). The design of experiments was employed to explore the optimal composition of the tablet. The similarity factor was employed to evaluate the equivalence in dissolution profiles between the test tablets and Glucophage XR as a reference. Bootstrap analysis was used to eliminate the formulations for which the dissolution profile was potentially inequivalent to that of the reference. The optimized tablet consisting of 150 mg of cetyl alcohol and 17% HPMC K15M showed a dissolution profile comparable with that of the reference with a similarity factor of 52.41, exhibited a floating lag time of less than 3 s in buffer media, remained floating for 24 h, and reduced the tablet weight by about 20% compared to that of the reference. The current study sheds light on the potential use of non-effervescent gastro-retentive extended-release tablets for high-dose drugs using a simple and efficient direct compression method, and as a potential alternative treatment for Glucophage XR. This study also highlights the importance of a systematic approach to formulation optimization and the evaluation of the dissolution profile.

Impact of hydrophilic binders on stability of lipid-based sustained release matrices of quetiapine fumarate by the continuous twin screw melt granulation technique

Dose dumping is the major drawback of sustained release (SR) matrices. The current research aimed to develop the stable lipid-based SR matrices of quetiapine fumarate (QTF) using Geleol™ (glyceryl monostearate; GMS) as the lipid matrix carrier and Klucel™ EF (HPC EF), Kollidon® VA64, and Kollidon® 12PF as hydrophilic binders. Formulations were developed using advanced twin screw melt granulation (TSMG) approach and the direct compression (DC) technique. Compared with the blends of DC, the granules of TSMG exhibited improved flow properties and tabletability. Solid-state characterization by differential scanning calorimetry of the prepared granules exhibited the crystalline nature of the lipid. Fourier transform infrared spectroscopy demonstrated no interaction between the formulation ingredients. The compressed matrices of TSMG and DC resulted in the sustained release of a drug over 16-24 h. Upon storage under accelerated conditions for 6 months, the matrices of TSMG retained their sustained release characteristics with no dose dumping in alcohol, whereas the matrices of DC resulted in the dose dumping of the drug attributing to the loss of matrix integrity and phase separation of lipid. Thus, it is concluded that the uniform distribution of a softened binder into a molten lipid carrier results in the stable matrices of TSMG.

Gel Strength of Hydrophilic Matrix Tablets in Terms of In Vitro Robustness

PURPOSE

The purpose of this study was to correlate the gel strength of swollen matrix tablets with their in vitro robustness against agitation intensity and applied mechanical forces. Five commercial products, i.e. Glucophage®, Alfuzosin®, Tromphyllin®, Preductal® MR and Quetiapin® formulated as water-soluble/erodible matrix tablets were investigated.

METHODS

Effect of agitation speed (50-150 rpm) on drug release, hydration/erosion and gel strength was investigated using USP paddle apparatus II. The gel strength of matrix tablets during dissolution at different conditions was characterized by a texture analyzer.

RESULTS

Commercial tablets formulated with HPMC of higher viscosity, such as K15M or K100M, demonstrated the gel strength in swollen state >0.02 MPa. In this case, the release mechanism was predominantly diffusional and, therefore, not affected by stirring speed and mechanical stress. In contrast, the Quetiapin® matrix tablet, formulated with HPMC K 4 M in amount of approx. 25%, demonstrated the gel strength dropped below 0.02 MPa after 6 h of release. In this case, the drug was predominantly released via erosional mechanism and very susceptible to stirring speed.

CONCLUSION

Sufficient gel strength of swollen tablets is an important prerequisite for unchanged in vitro performance in consideration of mechanical stress.

Are the release characteristics of Erzhi pills in line with traditional Chinese medicine theory? A quantitative study

OBJECTIVE

Traditional Chinese medicine (TCM) has been widely used throughout China to prevent and cure diseases for thousands of years, and now it is a part of the integrative medicine field that is available in Western societies. To ensure the safety and quality of the herbal medicines that are a major part of the TCM tradition, they must be held to modern pharmaceutical standards. Erzhi pill (EZP) is a Chinese Pharmacopeia-listed herbal preparation that is used in the long-term clinical management of post-menopausal symptoms, osteoporosis and menstrual disorders. Until now, whether the drug release mechanism of EZP is in line with its intended TCM usage has not been studied.

METHODS

The release of specnuezhenide from three EZPs (self-made, Leiyunshang and Renhe) in simulated gastric fluid (SGF), acetate buffer (pH 4.5 buffer) and simulated intestinal fluid (SIF) was investigated in a dissolution test. The water uptake capacity and erosion extent of the three EZPs were investigated using swelling and erosion studies. The drug release mechanism was further assessed through statistical model fitting, using DDSolver software.

RESULTS

The release of specnuezhenide from all three EZPs in SGF was less than 50% within a 4 h period. However, over 70% of the specnuezhenide was released from each EZP in both pH 4.5 buffer and SIF in the same time. Analysis of the swelling and erosion behaviors and the drug release mechanism of the three EZPs confirmed that the release rate from EZP followed a sustained release profile, which was an interactive combination of swelling and erosion.

CONCLUSION

This study showed that the release pattern from the pills was in line with the intended TCM use of EZP. TCM had not only theoretically considered sustained release from the pills, but also formulated them to achieve this release pattern. When establishing quality control standards for pills, the theoretical TCM usage and the actual release patterns need to be considered.

Dynamic structure model of polyelectrolyte complex based controlled-release matrix tablets visualized by synchrotron radiation micro-computed tomography

Hydrophilic matrix tablets are the most commonly used dosage forms to fabricate oral controlled-release systems. It is highly desirable to design delivery system with novel mechanism to achieve sustained drug release through a simplified preparation process. The chitosan-anionic polymers based matrix tablets is assumed to produce self-assembly in the gastrointestinal tract, then transferring into film-coated tablets from original matrix type. But its dynamic behavior during dissolution process and the on-going internal microstructural changes during drug release were still in the dark. In this study, by using synchrotron radiation X-ray micro-tomography (SR-μCT) with phase contrast imaging, the micro-structure characteristics of chitosan-λ-carrageenan (CS-λ-CG) matrix based tablets during the dissolution were successfully elucidated for the first time. The qualitative and quantitative analyses of intensity distribution distinguished a hydrated CS-λ-CG layer from a solid core. Visualization based on 3D models provided quantitative details on the micro-structural characteristics of hydration dynamics. After CS-λ-CG matrix tablets were immersed in simulated gastric fluid (SGF) pH 1.2 medium for 0.5-2.0 h, the hydrated layer transformed into a gel layer and a solid swollen layer. The erosion front, swelling front, and solvent penetration front were also defined from the distinguishable micro-structures. More importantly, once the matrix tablet was transferred from SGF to the simulated intestinal fluid (SIF) pH 6.8 medium, a new layer with the enhanced strength and compactness in comparison to common gels was formed on the surface of tablets. The temporal and spatial variation of 3D models further provided direct evidence for this cross-linking behavior, the new layer was composed of CS-λ-CG polyelectrolyte complexes (PEC) which subsequently dominated release mechanisms. In summary, the phase contrast SR-μCT technique was utilized to investigate the hydration dynamics of CS-λ-CG matrix tablets which was supposed to provide a novel drug release mechanism. Based on the structure feature obtained from the high contrast image, different hydration region was distinguished and the cross-linked film was identified and visualized directly for the first time.

Polyethylene oxide and its controlled release properties in hydrophilic matrix tablets for oral administration

Polymers are excipients that modify the rate of drug release from pharmaceutical dosage forms. Hydrophilic polymer-based controlled drug delivery system is more advantageous as compared to the conventional delivery system as it reduces the dosing frequency, improves therapeutic efficacy, reduces side-effects, and probably enhances patient compliance. Polyethylene oxide (PEO), a nonionic hydrophilic polymer, is one of the most widely used polymers for extending the drug release. This review mainly focuses on the PEO marketed by, but not limited to, The Dow Chemical Company under the trade name of POLYOX^TM. It is commercially available polyethylene oxide polymer existing in various molecular weight and viscosity grades depending upon the application. This study essentially discusses chemistry, physicochemical properties, and the impact of formulation and processing variables on the release of drug from hydrophilic PEO matrix tablets. Moreover, it also summarizes the stability, patents, and regulatory perspectives of POLYOX that can further influence the future developments of controlled release dosage forms.

Fabrication of extended-dissolution divalproex tablets: a green solvent-free granulation technique

Objective: Divalproex sodium (DVS) is a challenging drug owing to its hygroscopicity, bitter taste, and short in vivo half-life. This study aims to produce stable taste masked DVS once daily tablets using solvent free hot melt granulation (HMG) process.Methods: A lab scale high shear mixer granulator employing six meltable lipid binders (compritol^®888 ATO, beeswax, gelucire^®50/13, precirol^® ATO5, stearyl alcohol, and geleol^®) was used for the preparation of tablets. Quality control tests were performed on granules and tablets, and Box-Behnken's design was adopted to investigate the effect of binder concentration, impeller speed, and granulation time on the drug dissolution. Shelf and accelerated stability evaluation, taste assessment, and in vivo pharmacokinetic study were conducted on the selected batches.Results: Results revealed that DVS tablets were successfully prepared, and that the in vitro dissolution of the drug was inversely proportional to the binder concentration. Beeswax and compritol^® tablets showed similar dissolution profiles to the marketed product Depakote^® 500 ER tablets (F1 < 15 and F2 > 50). The selected batches showed lower moisture content (<2%) and successfully masked the bitter taste compared to uncoated tablets based on a hydrophilic matrix. The in vivo pharmacokinetic study delineated relative bioavailability values for Beeswax and Compritol^® tablets of 95.6% and 118%, respectively, compared to the marketed product.Conclusion: The solvent free HMG process can be employed to formulate 24 h extended dissolution DVS tablets with masked bitter taste and high stability, and comparable or higher bioavailability than the marketed product.

Static and dynamic structural features of single pellets determine the release behaviors of metoprolol succinate sustained-release tablets

The multiple-unit sustained-release (MUSR) dosage forms containing numerous sustained-release subunits present a reliable choice for oral formulation of controlled release systems. As a typical MUSR, the metoprolol succinate sustained-release tablet is an advanced system with limited researches devoted to relating its structure to the drug release phase other than the preparation process and modulation to the release behaviors. This research details a three-dimension method to image the internal structure and detail drug release features of commercial metoprolol succinate sustained-release tablets and component individual single pellets. As such, a new perspective for MUSR dosage form is provided. Using high energy synchrotron radiation X-ray microcomputed tomography (SR-μCT), the in-situ structure parameters were obtained nondestructively. It was demonstrated that the average number of spherical pellets in a tablet was 853 ± 12 (n = 3). The average volume of the pellets was 0.09 ± 0.01 mm3, the diameter was 0.55 ± 0.03 mm, and the sphericity was 0.87 ± 0.06. These data reflected the numerical features of pellets in MUSR tablets, which were helpful for reverse engineering to MUSR. Based on the three dimensional model generated by image processing and analysis software, the pellet structures were divided into three layers of typical depot sustained release system: pellet core, drug-containing layer and outer film. The dynamic structural features determined refer to the changes of structures in pellets during in vitro drug release, with evidence that the coating layer on the pellets maintained a spherical morphology whilst numerous valleys appeared on the surface. The material constitution and distribution in coating layer were evaluated by synchrotron radiation-based Fourier transform infrared mapping and results indicated a composition of hydroxypropyl methylcellulose dispersed in ethyl cellulose. Knowledge of these structural characteristics confirmed that the mechanism of sustained drug release was membrane controlled and consistent with the drug release profiles. In conclusion, the structural investigation provided knowledge of the intrinsic quality of metoprolol succinate sustained-release tablets and offers guidance for reverse engineering of MUSR.

Mechanical strength, structural and hydration properties of ethanol-treated starch tablets and their impact on the release of active ingredients

Ethanol-treated starch (ETS) shows potentiality to be used for binder of pharmaceutical tablets. This study was aimed to evaluate the mechanical strength, structural and hydration properties of ETS tablets and ETS tablets containing lauric acid and ascorbic acid and their release behavior. ETS was prepared from cassava starch at the temperatures of 80, 90, and 100 °C. The active compounds were entrapped within the ETS tablets by two methods, including dry mixing and ethanol solubilisation. The results indicated that ETS tablets from temperatures of 80 °C showed granular shapes, had high friability and low crushing strength indexes, and dispersed and released active ingredients rapidly upon contact with water. Meanwhile, ETS tablets from temperatures of 90 and 100 °C exhibited non-granular particles, had low friability and high crushing strength indexes. Upon hydration, the tablets of non-granular ETS containing lauric acid eroded gradually and released active ingredients during tablet's erosion, meanwhile ascorbic acid diffused out gradually from the swelled tablets.

Multi-dimensional visualization for the morphology of lubricant stearic acid particles and their distribution in tablets

The shapes of particles and their distribution in tablets, controlled by pretreatment and tableting process, determine the pharmaceutical performance of excipient like lubricant. This study aims to provide deeper insights to the relationship of the morphology and spatial distribution of stearic acid (SA) with the lubrication efficiency, as well as the resulting tablet property. Unmodified SA particles as flat sheet-like particles were firstly reprocessed by emulsification in hot water to obtain the reprocessed SA particles with spherical morphology. The three-dimensional (3D) information of SA particles in tablets was detected by a quantitative and non-invasive 3D structure elucidation technique, namely, synchrotron radiation X-ray micro-computed tomography (SR-µCT). SA particles in glipizide tablets prepared by using unmodified SA (GUT), reprocessed SA (GRT), as well as reference listed drug (RLD) of glipizide tablets were analyzed by SR-µCT. The results showed that the reprocessed SA with better flowability contributed to similarity of breaking forces between that of GRT and RLD. SA particles in GRT were very similar to those in RLD with uniform morphology and particle size, while SA particles in GUT were not evenly distributed. These findings not only demonstrated the feasibility of SR-µCT as a new method in revealing the morphology and spatial distribution of excipient in drug delivery system, but also deepened insights of solid dosage form design into a new scale by powder engineering.

Alfuzosin hydrochloride-loaded low-density gastroretentive sponges: development, in vitro characterization and gastroretentive monitoring in healthy volunteers via MRI

The current work aimed to develop low-density gastroretentive sponges loaded with alfuzosin HCl (ALF) to sustain the rate of drug release, improve its oral bioavailability and deliver it to the main site of absorption. Sponges were developed, according to a 2³ full factorial design, by compression of the lyophilized ALF-loaded hydroxypropylmethylcellulose (HPMC) or chitosan (CH) solutions. The influences of the polymer type, grade and concentration on the appearance, topography, porosity, density, in vitro ALF release, floating behavior, swelling, erosion, and mucoadhesive potential of the developed sponges were explored. Based on the desirability value, the best achieved system was selected. The gastroretentive potential of this system was evaluated in healthy male volunteers via MRI. Soft and flexible sponges were developed. They were characterized with interconnecting pores and channels and had excellent floating properties with respect to floating lag time and duration. Compared to HPMC-based sponges, CH-based ones exhibited higher porosity, larger pore diameters, lower bulk densities, higher drug release rates, larger swelling ratios, faster erosion rates and better mucoadhesive properties. MRI of magnetite-loaded best-achieved CH-based system (F8) ascertained the development of a promising gastroretentive system; exhibiting a gastric residence period of at least 5 h.

Food material properties as determining factors in nutrient release during human gastric digestion: a review

The fundamental mechanisms of nutrient release from solid foods during gastric digestion consists of multiple elementary processes. These include the diffusion of gastric juice into the food matrix and its simultaneous enzymatic degradation and mechanical breakdown by the peristaltic activity of the stomach. Understanding the relative role of these key processes, in association with the composition and structure of foods, is of paramount importance for the design and manufacture of novel foods possessing specific target behavior within the body. This review covers the past and current literature with respect to the in-stomach processes leading to physical and biochemical disintegration of solid foods and release of nutrients. The review outlines recent progress in experimental and modeling methods used for studying food disintegration mechanisms and concludes with a discussion on potential future research directions in this field. Information from pharmaceutical science-based modeling approaches describing nutrient release kinetics as a result of food disintegration in the gastric environment is also reviewed. Future research aimed at understanding gastric digestion is important not only for setting design principles for novel food design but also for understanding mechanisms underpinning dietary guidelines to consume wholesome foods.

Assessment of the effect of polymers combination and effervescent component on the drug release of swellable gastro-floating tablet formulation through compartmental modeling-based approach

The aim of this research was to assess the effect of polymer blend and effervescent components on the floating and swelling behaviors of swellable gastro-floating formulation as well as the drug release through a compartmental modeling analysis. Swellable gastro-floating formulation of freely water-soluble drug, metformin HCl as a drug model, was formulated and developed using D-optimal design. Polymer combination between interpolymer complex (IPC) (poly-vinyl acetate-copolymer methacrylate) and hydroxy propyl methyl cellulose (HPMC), and effervescent components were studied and optimized in this work. Several factors affecting the drug release behavior were determined e.g. swelling behavior, erosion behavior, and floating behavior were studied as well as the drug release through compartmental modeling analysis. The results revealed that the hydrophilic polymer was responsible for gas entrapment formed from effervescent reaction, meanwhile IPC contributed on maintaining the swollen matrix integrity through intermolecular polymer interaction. In addition, effervescent components played fundamental role in the formation of porous system as well as inducing burst release effect. Compartmental modeling provided different outlook about the drug release. Presence of IPC at a high proportion (10-15%) of the polymer blend modulated the changes of pattern of the drug release kinetics and mechanism. Finally, compartmental modeling-based approach was more adequate to describe the drug release kinetics and mechanism compared to the monophasic equation model correlating with process understanding of the drug release from swellable gastro-floating formulation.

Morphological characteristics and microstructure of kidney stones using synchrotron radiation μCT reveal the mechanism of crystal growth and aggregation in mixed stones

Understanding the mechanisms of kidney stone formation, development patterns and associated pathological features are gaining importance due to an increase in the prevalence of the disease and diversity in the presentation of the stone composition. Based on the microstructural characteristics of kidney stones, it may be possible to explain the differences in the pathogenesis of pure and mixed types of stones. In this study, the microstructure and distribution of mineral components of kidney stones of different mineralogy (pure and mixed types) were analyzed. The intact stones removed from patients were investigated using synchrotron radiation X-ray computed microtomography (SR-μCT) and the tomography slice images were reconstructed representing the density and structure distribution at various elevation planes. Infrared (IR) spectroscopes, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to confirm the bulk mineral composition in the thin section stones. Observations revealed differences in the micro-morphology of the kidney stones with similar composition in the internal 3-D structure. Calcium oxalate monohydrate stones showed well-organised layering patterns, while uric acid stones showed lower absorption signals with homogenous inner structure. Distinct mineral phases in the mixed types were identified based on the differential absorption rates. The 3-D quantitative analysis of internal porosity and spatial variation between nine different types of stones were compared. The diversity among the microstructure of similar and different types of stones shows that the stone formation is complex and may be governed by both physiological and micro-environmental factors. These factors may predispose a few towards crystal aggregation and stone growth, while, in others the crystals may not establish stable attachment and/or growth.

Tenofovir Hot-Melt Granulation using Gelucire® to Develop Sustained-Release Vaginal Systems for Weekly Protection against Sexual Transmission of HIV

Hot-melt granulation is a technique used to obtain granules by dispersing a drug in polymers at a high temperature. Tenofovir, an antiretroviral drug with proven activity as a vaginal microbicide, was dispersed in melted Gelucire® (or a mixture of different Gelucire®) to obtain drug-loaded granules. Studies performed on the granules proved that the drug is not altered in the hot-melt granulation process. The granules obtained were included in a matrix formed by the hydrophilic polymers hydroxypropylmethylcellulose and chitosan to obtain vaginal tablets that combine different mechanisms of controlled release: The Gelucire® needs to soften to allow the release of the Tenofovir, and the hydrophilic polymers must form a gel so the drug can diffuse through it. The studies performed with the tablets were swelling behavior, Tenofovir release, and ex vivo mucoadhesion. The tablets containing granules obtained with Tenofovir and Gelucire® 43/01 in a ratio of 1:2 in a matrix formed by hydroxypropylmethylcellulose and chitosan in a ratio of 1.9:1 were selected as the optimal formulation, since they release Tenofovir in a sustained manner over 216h and remain attached to the vaginal mucosa throughout. A weekly administration of these tablets would therefore offer women protection against the sexual transmission of HIV.

Optimization of taste-masking on ibuprofen microspheres with selected structure features

The microsphere was a primary particulate system for taste-masking with unique structural features defined by production process. In this article, ibuprofen lipid microspheres of octadecanol and glycerin monostearate were prepared to mask the undesirable taste of ibuprofen via three kinds of spray congealing processes, namely, air-cooling, water-cooling and citric acid solution-cooling. The stereoscopic and internal structures of ibuprofen microspheres were quantitatively analyzed by synchrotron radiation X-ray micro-computed tomography (SR-µCT) to establish the relationship between the preparation process and microsphere architectures. It was found that the microstructure and morphology of the microspheres were significantly influenced by preparation processes as the primary factors to determine the release profiles and taste-masking effects. The sphericity of ibuprofen microspheres congealed in citric acid solution was higher than that of other two and its morphology was more regular than that being congealed in air or distilled water, and the contact angles between congealing media and melted ibuprofen in octadecanol and glycerin monostearate well demonstrated the structure differences among microspheres of three processes which controlled the release characteristics of the microspheres. The structure parameters like porosity, sphericity, and radius ratio from quantitative analysis were correlated well with drug release behaviors. The results demonstrated that the exterior morphology and internal structure of microspheres had considerable influences on the drug release behaviors as well as taste-masking effects.

An overview on the mathematical modeling of hydrogels' behavior for drug delivery systems

Hydrogels-based systems (HBSs) for drug delivery are nowadays extensively used and the interest in modeling their behavior is dramatically increasing. In this review a critical overview on the modeling approaches is given, quantitatively and qualitatively analyzing the publications on the subject, the trend of the publications per year and the type of modeling approaches. It was found that, despite the drug release fitting models (i.e. Higuchi's equation) are the most abundant, their use for HBSs is decreasing in the last years and luckily, considering the limiting assumption on which they were built, they will be confined to simple mathematical fitting equations. Within the mechanistic models the "multi-component" with the swelling approximation (mass transport only) and with the mechanics (fully coupled) are experiencing the highest growth rate, with much more interest toward the last one that, in the next years could be able to provide a first principles model. Statistical models, especially based on the response surface methodology, are rapidly spreading in the scientific community mainly thanks to their ability to be predictive, regardless of the phenomenology, in the analyzed design space with very low efforts. Neural Networks models for HBSs, in countertrend with their use in the pharmaceutical industry, have never take off preferring less data demanding statistical models.

HIFU induced particles redistribution in polymer matrix via synchrotron radiation X-ray microtomography

High-intensity Focused Ultrasound (HIFU) was used to stimulate the embedded copper sulfate (CuSO₄) particles to release from the crosslinked poly (methyl methacrylate-co-butyl acrylate) copolymer solid matrix. In order to better understand the ultrasound release mechanism for drug/polymer delivery systems, the synchrotron radiation X-ray computed microtomography (SR-CT) was used to non-destructively investigate the structure of drug/polymer delivery systems after different HIFU treatment time. For the first time, we clearly demonstrate that ultrasonic waves can overcome the constraints of the polymer chain and drive the filler to move from the strong region to the weak region in the solid polymer matrix, thus resulting in a change in distribution of the filler in solid polymers. This result also demonstrates that SR-CT is a powerful technique which can be used to quantitatively study the 3D structure of fillers/polymers composite as it can take a broader and overall view than the conventional localized two-dimensional analysis method such as SEM, TEM.

3D printed, controlled release, tritherapeutic tablet matrix for advanced anti-HIV-1 drug delivery

PURPOSE

A 3D-Bioplotter® was employed to 3D print (3DP) a humic acid-polyquaternium 10 (HA-PQ10) controlled release fixed dose combination (FDC) tablet comprising of the anti-HIV-1 drugs, efavirenz (EFV), tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC).

METHODS

Chemical interactions, surface morphology and mechanical strength of the FDC were ascertained. In vitro drug release studies were conducted in biorelevant media followed by in vivo study in the large white pigs, in comparison with a market formulation, Atripla®. In vitro-in vivo correlation of results was undertaken.

RESULTS

EFV, TDF and FTC were successfully entrapped in the 24-layered rectangular prism-shaped 3DP FDC with a loading of ∼12.5 mg/6.3 mg/4 mg of EFV/TDF/FTC respectively per printed layer. Hydrogen bonding between the EFV/TDF/FTC and HA-PQ10 was detected which was indicative of possible drug solubility enhancement. The overall surface of the tablet exhibited a fibrilla structure and the 90° inner pattern was determined to be optimal for 3DP of the FDC. In vitro and in vivo drug release profiles from the 3DP FDC demonstrated that intestinal-targeted and controlled drug release was achieved.

CONCLUSION

A 3DP FDC was successfully manufactured with the aid of a 3D-Bioplotter in a single step process. The versatile HA-PQ10 entrapped all drugs and achieved an enhanced relative bioavailability of EFV, TDF, and FTC compared to the market formulation for potentially enhanced HIV treatment.

Optimization of tenofovir release from mucoadhesive vaginal tablets by polymer combination to prevent sexual transmission of HIV

The use of sustained-release mucoadhesive vaginal tablets of antiretroviral drugs as microbicidal formulations can be an effective strategy for reducing the sexual transmission of HIV from men to women, which is a main problem particularly in low- and middle-income countries. Different polymers (hydroxypropylmethyl cellulose (HPMC), chitosan, guar gum and Eudragit^® RS) have proven some good features for this purpose. At this work, these polymers have been combined in pairs in different proportions to enhance the advantages offered by each one individually. The in vitro release of tenofovir from the matrices, ex vivo mucoadhesive capacity (evaluated on vaginal mucosa) and the degree of swelling in simulated vaginal fluid have been assessed. A multimodal pore size distribution is observed in porosimetry studies -carried out with swelling witnesses-, due to the contribution of polymers with different swelling behaviour to the pore formation, and it is corroborated by scanning electron microscopy. X-ray diffraction technique confirms the changes in crystallinity of the formulation after swelling. We can report that the combination of HPMC and chitosan in the same formulation may be useful for the prevention of sexual transmission of HIV, since tablets can be obtained that remain adhered to the vaginal mucosa for 96h, so the drug is released in a sustained manner for 72h. When the formulation contains more chitosan than HPMC the swelling is moderate, making it more comfortable for women to apply.

Correlation between the viscoelastic properties of the gel layer of swollen HPMC matrix tablets and their in vitro drug release

Drug release from hydroxypropyl methylcellulose (HPMC) hydrophilic matrix tablets is controlled by drug diffusion through the gel layer of the matrix-forming polymer upon hydration, matrix erosion or combination of diffusion and erosion mechanisms. In this study, the relationship between viscoelastic properties of the gel layer of swollen intact matrix tablets and drug release was investigated. Two sets of quetiapine fumarate (QF) matrix tablets were prepared using the high viscosity grade HPMC K4M at low (70 mg/tablet) and high (170 mg/tablet) polymer concentrations. Viscoelastic studies using a controlled stress rheometer were performed on swollen matrices following hydration in the dissolution medium for predetermined time intervals. The gel layer of swollen tablets exhibited predominantly elastic behavior. Results from the in vitro release study showed that drug release was strongly influenced by the viscoelastic properties of the gel layer of K4M tablets, which was further corroborated by results from water uptake studies conducted on intact tablets. The results provide evidence that the viscoelastic properties of the gel layer can be exploited to guide the selection of an appropriate matrix-forming polymer, to better understand the rate of drug release from matrix tablets in vitro and to develop hydrophilic controlled-release formulations.

In situ 3D topographic and shape analysis by synchrotron radiation X-ray microtomography for crystal form identification in polymorphic mixtures

Polymorphism denotes the existence of more than one crystal structure of a substance, and great practical and theoretical interest for the chemical and pharmaceutical industries. In many cases, it is challenging to produce a pure crystal form and establish a sensitive detection method for the identification of crystal form in a mixture of polymorphs. In this study, an accurate and sensitive method based on synchrotron radiation X-ray computed microtomography (SR-μCT) was devised to identify the polymorphs of clopidogrel bisulphate (CLP). After 3D reconstruction, crystal particles were extracted and dozens of structural parameters were calculated. Whilst, the particle shapes of the two crystal forms were all irregular, the surface of CLP II was found to be rougher than CLP I. In order to classify the crystal form based on the quantitative morphological property of particles, Volume Bias Percentage based on Surface Smoothing (VBP) was defined and a new method based on VBP was successfully developed, with a total matching rate of 99.91% for 4544 particles and a lowest detectable limit of 1%. More important for the mixtures in solid pharmaceutical formulations, the interference of excipients can be avoided, a feature cannot achieved by other available analytical methods.

Visualization and quantification of deformation behavior of clopidogrel bisulfate polymorphs during tableting

The deformation behavior of particles under pressure dominates the mechanical properties of solid dosage forms. In this study, the in situ 3D deformation of two polymorphs (I and II) of clopidogrel bisulfate (CLP) was determined to illustrate pressure distribution profiles within the tablet by the deformation of the crystalline particles for the first time. Synchrotron radiation X-ray computed microtomography (SR-μCT) was utilized to visualize and quantify the morphology of thousands crystalline particles of CLP I and CLP II before and after compression. As a result, the deformation was examined across scale dimensions from microns to the size of the final dosage form. Three dimensional parameters such as volume, sphericity, oblate and prolate of individual particle and distributions were computed and analyzed for quantitative comparison to CLP I and CLP II. The different degrees of deformation under the same compression conditions of CLP I and CLP II were observed and characterized quantitatively. The map of deformation degrees within the tablet illustrated the heterogeneous pressure distribution in various regions of the compacted tablet. In conclusion, the polymorph deformation behaviors demonstrated by SR-μCT quantitative structure analysis deepen understanding of tableting across dimensions from microns to millimeters for the macrostrcuture of tablet.

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.

Release behaviour of single pellets and internal fine 3D structural features co-define the in vitro drug release profile

Multi-pellet formulations are advantageous for the controlled release of drugs over single-unit dosage forms. To understand the diffusion controlled drug release mechanism, the pellet structure and drug release from a single pellet (not at dose level) were studied using synchrotron radiation X-ray computed microtomography (SR-μCT) and a sensitive LC/MS/MS method. The purpose of this article is to introduce a powerful, non-invasive and quantitative technique for studying individual pellet microstructures and to investigate the relationship between the microstructure and drug release from single pellets. The data from the single pellet dissolution measurements demonstrated that the release profile of capsules containing approximately 1,000 pellets per unit dose was the summation of the release profiles of the individual pellets. The release profiles of single tamsulosin hydrochloride (TSH) pellets formed three groups when a cluster analysis was performed, and the dissolution rate of the individual pellets correlated well with the combined effects of the drug loading, volume and surface area of the pellets (R(2) = 0.9429). In addition, the void microstructures within the pellet were critical during drug release. Therefore, SR-μCT is a powerful tool for quantitatively elucidating the three-dimensional microstructure of the individual pellets; because the microstructure controls drug release, it is an important parameter in the quality control of multi-pellet formulations.