Three dimensional structural insight of laser drilled orifices in osmotic pump tablets

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.

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.

Predictive selection rule of favourable image processing methods for X-ray micro-computed tomography images of tablets

Adequately processed X-ray micro-computed tomography images of real pharmaceutical formulations provide the possibility to validate in silico tools for the prediction of disintegration and/or dissolution. However, the evaluation of suitable image processing pathways is time consuming. The objective of this study was to prove the transferability of image processing methods and to develop an approach to select probable favourable image processing approaches for data sets with similar properties to accelerate the evaluation process. Therefore, data from a previously performed evaluation of image processing approaches and parameters were used to analyse the robustness of the image processing by statistical resampling and to develop a predictive rule set. The rule set was verified by both one new ratio of API and excipient within and outside of the ratios used to develop the rule. The rule was applied to images of a binary mixture with new compounds with similar determined image properties to prove the transferability of the rule set. It was possible to identify robust image processing pathways with narrow ranges of input parameters. The prediction of the image processing pathways led to high desirabilities which were confirmed by visual verification for ratios within the calibrated range. The transfer to the new binary mixture was successful and confirmed as well.

Evaluation of different segmentation methods of X-ray micro computed tomography images

In silico tools for the prediction of disintegration and/or dissolution of tablets can be validated using adequate images of real pharmaceutical formulations. X-ray micro-computed tomography images of 12 different tablet batches prepared from binary mixtures of API and excipient were used. The goal of this work was to compare different segmentation methods to improve the results and processing time of an evaluation of pre-processing methods. The open source software ImageJ was utilised for the image processing. Different threshold algorithms were applied as well as different cluster numbers for the k-means clustering. The pathways were analysed regarding their desirability which was calculated from the recovery rates and their ratios. It was possible to identify suitable pathways for each single batch as well as for combinations of several batches. The recovery rates of the best pathways were always approximately 100%. It was possible to confirm the correctness of the image processing by visual perception. The image processing could be improved and sped up.

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.

Recent advances of novel technologies for quality consistency assessment of natural herbal medicines and preparations

Quality consistency is one of the basic attributes of medicines, but it is also a difficult problem that natural medicines and their preparations must face. The complex chemical composition and comprehensive pharmacological action of natural medicines make it difficult to simply apply the commonly used evaluation methods in chemical drugs. It is thus urgent to explore the novel evaluation methods suitable for the characteristics of natural medicines. With the rapid development of analytical techniques and the deepening understanding of the quality of natural herbs, increasing numbers of researchers have proposed many new ideas and technologies. This review mainly focuses on the basic principles, technical characteristics and application examples of the chemical evaluation, biological evaluation methods and their combination in quality consistency evaluation of natural herbs. On the bases of chemical evaluation and clinical efficacy, new methods reflecting their pharmacodynamic mechanism and safety characteristics will be developed, and gradually towards accurate quality control, to achieve the goal of quality consistency. We hope that this manuscript can provide new ideas and technical references for the quality consistency of natural drugs and their preparations, thus better guarantee their clinical efficacy and safety, and better promote industrial development.

Double-layered osmotic pump controlled release tablets of actarit: In vitro and in vivo evaluation

The aim of the study was to develop actarit double-layered osmotic pump tablets to overcome the weak points of actarit common tablets, such as short half-life and large plasma concentration fluctuations. Single factor experiment and orthogonal test were applied to optimize the formulation; the pharmacokinetic study was performed in beagle dogs adopting actarit common tablets as reference tablets. The optimal formulation was as follows: drug layer: 150 mg actarit, 240 mg PEO-N80, 50 mg NaCl; push layer: 140 mg PEO-WSR303, 20 mg NaCl; coating solution: 30 g cellulose acetate and 6 g PEG 4000 in 1000 ml 94% acetone solution, 60 mg coating weight gain. The pharmacokinetic study showed that T_max was prolonged by the contrast of commercial common tablets with constant drug release rate, but the bioavailability was equivalent. And a good in vivo–in vitro correlation of the actarit osmotic pump tablets was also established. The designed actarit osmotic pump tablets can be applied for rheumatoid arthritis, proposing a promising replacement for the marked common products.