Origin of profound changes in powder properties during wetting and nucleation stages of high-shear wet granulation of microcrystalline cellulose

Evaluation of binders in twin-screw wet granulation - Optimization of tabletability

The influence of hydroxypropyl cellulose type (HPC-SSL SFP, HPC-SSL), concentration (2 %, 3.5 %, 5 %) and filler (lactose, calcium hydrogen phosphate (DCP)/microcrystalline cellulose (MCC)) on twin-screw wet granulation and subsequent tableting was studied. The aim was to identify the formulation of the highest tabletability which still fulfills the requirements of the disintegration. Lactose combined with 5 % binder enabled a higher tabletability and a faster disintegration than DCP/MCC. It was found that tabletability of lactose formulations can be increased by higher binder concentration and higher compression pressure while tabletability of DCP/MCC formulations can be only increased by higher compression pressure. It was observed that batches containing DCP/MCC failed the disintegration test, if the highest binder concentration and the highest compression pressure were used. To ensure a fast disintegration, the compression pressure or at least the binder concentration had to be low. Changing the disintegrant and its localization improved the DCP/MCC formulation, resulting in faster disintegration than lactose tablets. However, it also resulted in a lower tabletability. In this study best tablets were achieved with 3.5 % or 5 % binder and lactose as filler. These tablets presented the highest tabletability but still disintegrated in less than 500 s.

Cylindrical granules in the development of mesalazine solid formulations (Ⅱ): The contribution of high aspect ratio to favorable tabletability

Recently, cylindrical granules have been applied in pharmaceutical fields and their aspect ratio (AR) is considered an important factor in the manufacturing process. However, the relationships between AR and the tableting process were seldom reported. This study aims to clarify the role of AR in the tableting process of cylindrical granules. First, mesalazine cylindrical granules with different AR were extruded, and their physical attributes were then comprehensively characterized. Subsequently, their compression behaviors and tableting performances were systematically assessed. Notably, it was found that the cylindrical granules with high AR possessed good anti-deformation capacity and favorable tabletability. Finally, the dissolution test suggested that tablets compressed from cylindrical granules with higher AR showed lower dissolution rates. Collectively, findings in this study identified that the AR of cylindrical granules was a critical factor in the tableting process and provided valuable guidance for the application of these granules in oral solid formulations.

Cylindrical granules in the development of mesalazine solid formulations (Ⅰ): Physical properties, compression behaviors, and tableting performances

Cylindrical granules have been employed in the pharmaceutical industry. However, to our knowledge, the study on the compressibility and tabletability of cylindrical granules has not been reported. This study aimed to explore the effects of the physical properties of cylindrical granules on the compression behaviors and the tableting performances, with mesalazine (MSZ) as a model drug. First, the six formulations of MSZ cylindrical granules were extruded by changing the ethanol proportion in the binder. Then, the physical characteristics of MSZ cylindrical granules were systematically studied. Subsequently, the compressibility and tabletability were evaluated using different mathematic models. It was worth noting that highly porous cylindrical granules possessed favorable compressibility and good tabletability due to the increased pore volume, reduced density, and decreased fracture forces. Finally, dissolution tests were conducted and highly porous granules showed higher dissolution rates than the less porous ones, but an opposite trend was observed for the corresponding tablets. This study proved the importance of physical properties in the tableting process of cylindrical granules and provided strategies to improve their compressibility and tabletability.

Alginate-based matrix tablets for drug delivery

INTRODUCTION

As a nature-derived polymer with swelling and gelling properties, alginate has found wide biopharma-relevant applications. However, there is comparatively limited attention on alginate in tablet formulations. Therefore, this review aimed to provide an overview of the applications of alginate in solid dosage form formulations.

AREAS COVERED

This review outlines the role of alginate for oral sustained release formulations. For better insights into its application in drug delivery, the mechanisms of drug release from alginate matrices are discussed alongside the alginate inherent properties and drug properties. Specifically, the influence of alginate properties and formulation components on the resultant alginate gel and subsequent drug release is reviewed. Modifications of the alginate to improve its properties in modulating drug release are also discussed.

EXPERT OPINION

Alginate-based matrix tablets is useful for sustaining drug release. As a nature-derived polymer, batch consistency and stability raise some concerns about employing alginate in formulations. Furthermore, the alginate gel properties can be affected by formulation components, pH of the dissolution environment and the tablet matrix micro-environment pH. Conscientious efforts are pivotal to addressing these formulation challenges to increase the utilization of alginate in oral solid dosage forms.

Varied Bulk Powder Properties of Micro-Sized API within Size Specifications as a Result of Particle Engineering Methods

Micronized particles are commonly used to improve the content uniformity (CU), dissolution performance, and bioavailability of active pharmaceutical ingredients (API). Different particle engineering routes have been developed to prepare micron-sized API in a specific size range to deliver desirable biopharmaceutical performance. However, such API particles still risk varying bulk powder properties critical to successful manufacturing of quality drug products due to different particle shapes, size distribution, and surface energetics, arising from the anisotropy of API crystals. In this work, we systematically investigated key bulk properties of 10 different batches of Odanacatib prepared through either jet milling or fast precipitation, all of which meet the particle size specification established to ensure equivalent biopharmaceutical performance. However, they exhibited significantly different powder properties, solid-state properties, dissolution, and tablet CU. Among the 10 batches, a directly precipitated sample exhibited overall best performance, considering tabletability, dissolution, and CU. This work highlights the measurable impact of processing route on API properties and the importance of selecting a suitable processing route for preparing fine particles with optimal properties and performance.

The effect of granules characters on mechanical properties of press-coated tablets: A comparative study

The aim of this study was to investigate the correlation between critical granules characters (including particle size, surface roughness, and apparent porosity) and mechanical properties of press-coated tablets. Granules of a model formulation were prepared through Roll Compaction Granulation (RCG), High Shear Granulation (HSG), and Fluidized Bed Granulation (FBG) to prepare granules with different surface roughness and apparent porosity. The surface roughness and porosity of granules had a significantly greater effect on mechanical properties than the particle size of granules. Whether for brittle or plastic materials, FBG granules with the roughest surface and the greatest apparent porosity exhibited the best compression properties. The elastic recovery test, the interlayer adhesion forces study, the break pattern test, and the X-ray microcomputed tomography investigation suggested that granules with great apparent porosity and rough surfaces could contribute to the production of stable press-coated structures. Moreover, for press-coated tablets prepared using granules, the proper granules in the coat layer could eliminate the side effect of the rigid core on the mechanical strength. The above understandings will be conducive to the selection of compatible and appropriate granules characters, which can enhance mechanical properties and extend the application of press-coated tablets.

Systematic Study of the Effects of High Shear Granulation Parameters on Process Yield, Granule Size, and Shape by Dynamic Image Analysis

The aim of the work was to analyze the influence of process parameters of high shear granulation on the process yield and on the morphology of granules on the basis of dynamic image analysis. The amount of added granulation liquid had a significant effect on all monitored granulometric parameters and caused significant changes in the yield of the process. In regard of the shape, the most spherical granules with the smoothest surface were formed at a liquid to solid ratio of ≈1. The smallest granules were formed at an impeller speed of 700 rpm, but the granules formed at 500 rpm showed both the most desirable shape and the highest process yield. Variation in the shape factors relied not only on the process parameters, but also on the area equivalent diameter of the individual granules in the batch. A linear relationship was found between the amount of granulation liquid and the compressibility of the granules. Using response surface methodology, models for predicting the size of granules and process yield related to the amount of added liquid and the impeller speed were generated, on the basis of which the size of granules and yield can be determined with great accuracy.

In vitro behavior of dronedarone hydrochloride loaded pellets using vacuum impregnation technique

Pharmaceutical pellets are a versatile and adaptable drug carrier system with pharmacological and technological advantages specific to multiparticulate delivery systems. Depending on their porosity and formulation procedure, a controlled drug release pattern can be achieved using a variety of pellet production and drug loading techniques. In the present paper, we have developed microcrystalline cellulose based porous pellets by extrusion/spheronization process. Two types of dronedarone hydrochloride suspensions were prepared in order to load drug onto carrier pellets using vacuum impregnation method. Despite its extensive use in the biomedical field of research, this technique hasn't been applied yet as means of incorporating drugs into inert and porous pellets. In addition, drug release control was tested by spray coating the pellets with hydroxypropyl methylcellulose in a fluidized bed. Pellet morphology, porosity and dissolution behavior were determined and the results indicate that DNR particle size affects the drug incorporation mechanism and, therefore, drug release patterns obtained through in vitro tests. Additionally, it was proven that polymer-based film-coat significantly slows down the drug release from the pellets. In vitro studies of the coated pellets in biorelevant fluids have shown that DNR release profiles are directly related to the type of dissolution media used. Vacuum impregnation was found to be promising technique for incorporation of DNR onto the surface of the porous pellets and into their pores.

A microcrystalline cellulose based drug-composite formulation strategy for developing low dose drug tablets

The uniformity of active pharmaceutical ingredient (API) is a main challenge associated with manufacturing low dose tablets. Here, we present a binder enhanced API-microcrystalline cellulose (BEAM) approach to address this challenge. In the BEAM approach a powder is prepared by spraying a PVP hydro-alcoholic solution, which contains API at an appropriate concentration, onto a powder bed of microcrystalline cellulose (MCC) under high shear. BEAM powders of 5 model APIs, with solubility spanning a range of 5 orders of magnitude, all exhibited excellent flowability, tabletability, and low ejection force. Therefore, all BEAM powders could be directly compressed into tablets with excellent API uniformity and fast disintegration without using any other excipients. Compared to traditional ways to address content uniformity problems, this formulation strategy is much more robust and simpler, making it a potential platform technology for manufacturing tablets of potent APIs.

Crystal and Particle Engineering Strategies for Improving Powder Compression and Flow Properties to Enable Continuous Tablet Manufacturing by Direct Compression

Continuous manufacturing of tablets has many advantages, including batch size flexibility, demand-adaptive scale up or scale down, consistent product quality, small operational foot print, and increased manufacturing efficiency. Simplicity makes direct compression the most suitable process for continuous tablet manufacturing. However, deficiencies in powder flow and compression of active pharmaceutical ingredients (APIs) limit the range of drug loading that can routinely be considered for direct compression. For the widespread adoption of continuous direct compression, effective API engineering strategies to address power flow and compression problems are needed. Appropriate implementation of these strategies would facilitate the design of high-quality robust drug products, as stipulated by the Quality-by-Design framework. Here, several crystal and particle engineering strategies for improving powder flow and compression properties are summarized. The focus is on the underlying materials science, which is the foundation for effective API engineering to enable successful continuous manufacturing by the direct compression process.

Mechanics of Pharmaceutical Pellets-Constitutive Properties, Deformation, and Breakage Behavior

To ensure robust manufacturing of unit-based oral solid dosage forms with minimal structural imperfections and high mechanical reliability across subsequent processing unit operations (e.g., withstanding mechanical stresses during coating, optional axial compression, handling, packaging, storage, and transport conditions), process design should include consideration of precise limits of accurate micro, macro, and bulk properties of the constituent pellets. This communication presents a comprehensive intricate database of micromechanical properties' and breakage probability distribution functions of pellets, illustrating the stiffening and strengthening effects of coatings and the softening and weakening effects of structural moisture. Further insights such as the (contact) history-dependent softening during decompression, strain hardening on repeated stressing, strength recovery by drying, and the fragmentation pattern by cracking are also presented. The contents herein are based on conveniently performable lab-scale diametrical compression measurements on model microcrystalline cellulose pellets-demonstrating feasibility of the approach and validity of the contribution.

Analysis of the origins of content non-uniformity in high-shear wet granulation

In this study, the origins of granule content non-uniformity in the high-shear wet granulation of a model two-component pharmaceutical blend were investigated. Using acetaminophen as the active pharmaceutical ingredient (API) and microcrystalline cellulose as the excipient, the distribution of the API across the granule size classes was measured for a range of conditions that differed in the duration of the initial dry mixing stage, the overall composition of the blend and the wet massing time. The coarse granule fractions were found to be systematically sub-potent, while the fines were enriched in the API. The extent of content non-uniformity was found to be dependent on two factors - powder segregation during dry mixing and redistribution of the API between the granule size fractions during the wet massing phase. The latter was demonstrated in an experiment where the excipient was pre-granulated, the API was added later and wet massed. The content non-uniformity in this case was comparable to that obtained when both components were present in the granulator from the beginning. With increasing wet massing time, the extent of content non-uniformity decreased, indicating that longer wet massing times might be a solution for systems with a natural tendency for component segregation.

The granule porosity controls the loss of compactibility for both dry- and wet-processed cellulose granules but at different rate

The aim of this study was to investigate the role of porosity on the compression behavior and tablet tensile strength for granules produced by a dry granulation procedure. Microcrystalline cellulose was used as a typical pharmaceutical excipient and a comparison was made with the effect of granule porosity on the compression behavior and tablet tensile strength of wet-processed granules of the same composition. Both the wet and dry granulation process caused a loss in compactibility of the material that was controlled by the granule porosity up to a critical point of porosity and friability. Above this threshold value of porosity, the granules nearly collapsed completely into primary particles during compression. In these cases, the micro-structure and tensile strength of the formed tablets resembled that of tablets formed from the original ungranulated powder.

Evolution of structure and properties of granules containing microcrystalline cellulose and polyvinylpyrrolidone during high-shear wet granulation

Granulation behavior of microcrystalline cellulose (MCC) in the presence of 2.5% polyvinylpyrrolidone (PVP) was systematically studied. Complex changes in flowability and tabletability of lubricated MCC granules are correlated to changes in intragranular porosity, morphology, surface smoothness, size distribution, and specific surface area (SSA). With 2.5% PVP, the use of 45% granulation water leads to 84% reduction in tablet tensile strength and 76% improvement in powder flow factor. The changes in powder performance are explained by granule densification and surface smoothing. The granulating water level corresponding to the onset of overgranulation, 45%, is significantly lower than the 70% water required for unlubricated MCC granules without PVP. At more than 45% water levels, MCC-PVP granules flow well but cannot be compressed into intact tablets. Such changes in powder performance correspond to the rapid growth into large and dense spheres with smooth surface. Compared with MCC alone, the onset of the phase of fast granule size enlargement occurs at a lower water level when 2.5% PVP is used. Although the use of 2.5% PVP hastens granule nucleation and growth rate, the mechanisms of overgranulation are the same, that is, size enlargement, granule densification, surface smoothing, and particle rounding in both systems.

Probing interfaces between pharmaceutical crystals and polymers by neutron reflectometry

Pharmaceutical powder engineering often involves forming interfaces between the drug and a suitable polymer. The structure at the interface plays a critical role in the properties and performance of the composite. However, interface structures have not been well understood due to a lack of suitable characterization tool. In this work, we have used ellipsometry and neutron reflectometry to characterize the structure of such interfaces in detail. Ellipsometry provided a quick estimate of the number of layers and their thicknesses, whereas neutron reflectometry provided richer structural information such as density, thickness, roughness, and intermixing of different layers. The combined information allowed us to develop an accurate model about the layered structure and provided information about intermixing of different layer components. Systematic use of these characterization techniques on several model systems suggests that the nature of the polymer had a small effect on the interfacial structure, while the solvent used in polymer coating had a large effect. These results provide useful information on the efforts of engineering particle properties through the control of the interfacial chemistry.

Initial moisture content in raw material can profoundly influence high shear wet granulation process

The aim of this work is to demonstrate that uncontrolled initial moisture content in microcrystalline cellulose (MCC) can profoundly affect high shear wet granulation (HSWG) process. We show that granule tabletability is reduced by approximately 50% when initial moisture content in MCC increases from 0.9% to 10.5% while all other processing parameters remain unchanged. An important observation is that granule tableting performance deteriorates significantly when initial moisture content increases from 2.6% to 4.9%, which is considered normal variation in moisture content for typical MCC (3-5%). The deteriorated tabletability is largely caused by increased granule size. On the other hand, granule flowability improves continuously with increasing initial moisture content in MCC. The improved flowability is mainly a result of granule size enlargement. Clearly, moisture content of raw materials for a HSWG process must be carefully monitored and controlled to ensure a robust manufacturing process as required by the quality-by-design principle.