Moistening liquid-dependent de-aggregation of microcrystalline cellulose and its impact on pellet formation by extrusion-spheronization

MUPS Tableting-Comparison between Crospovidone and Microcrystalline Cellulose Core Pellets

Multi-unit pellet system (MUPS) tablets were fabricated by compacting drug-loaded pellets of either crospovidone or microcrystalline cellulose core. These pellets were produced by extrusion-spheronization and coated with ethylcellulose (EC) for a sustained drug release function. Coat damage due to the MUPS tableting process could undermine the sustained release function of the EC-coated pellets. Deformability of the pellet core is a factor that can impact the extent of pellet coat damage. Thus, this study was designed to evaluate the relative performance of drug-loaded pellets prepared with either microcrystalline cellulose (MCC) or crospovidone (XPVP) as a spheronization aid and were comparatively evaluated for their ability to withstand EC pellet coat damage when compacted. These pellets were tableted at various compaction pressures and pellet volume fractions. The extent of pellet coat damage was assessed by the change in drug release after compaction. The findings from this study demonstrated that pellets spheronized with XPVP had slightly less favorable physical properties and experienced comparatively more pellet coat damage than the pellets with MCC. However, MUPS tablets of reasonable quality could successfully be produced from pellets with XPVP, albeit their performance did not match that of vastly mechanically stronger pellets with MCC at higher compaction pressure.

The Effect of Thermal-Treating on Drug Release from Sustained Release Alginate-Eudragit RS Matrices

Purpose: The main objective of the present study was to develop the colonic delivery system for 5-aminosalicylic acid (5-ASA) as an anti-inflammatory drug.

Methods: Matrix pellets containing various proportions of alginate, calcium and Eudragit^® RS were prepared by extrusion-spheronization technique. Thermal treatment was used to investigate the effect of the curing process on the surface morphology, mechanical and physicochemical properties and in vitro drug release profile of pellets. Based on the obtained results optimal formulations were selected to coating by the Eudragit^® RS and subjected to a subsequent continuous dissolution test.

Results: Image analysis and also scanning electron microscopy results proved acceptable morphology of the pellets. The fourier transform infrared spectroscopy and differential scanning calorimetry studies ruled out any interactions between the formulation’s components. Curing process did not alter the mechanical properties of pellets. The release rate of the drug from matrices was prolonged due to the decreased porosity of cured pellets. Furthermore, selected cured pellets which coated with Eudragit^® RS, prevented undesired premature drug release.

Conclusion: Formulation containing 17.5% calcium, 17.5% alginate, and a coating level of 10% demonstrated enhanced drug release so that provided resistance to acidic conditions, allowing complete drug release in alkaline pH, mimicking colonic environment. The slow and consistent drug release from this formulation could be used for treatment of a broader range of Inflammatory bowel disease (IBD) patients especially in whom colonic pH levels have been measured at lower than pH 7.0.

Elucidation of mass transfer mechanisms in pellet formation by spheronization

Previously published mechanisms of pellet formation during extrusion-spheronization include a transfer of material between different granules. This research aimed to specify the origin of this transfered mass, enabling further insight into the extrusion-spheronization process. Granules of various diameters were rounded simultaniously in a spheronizer to ascertain if mass transfer between smaller and larger granules is truly in balance, or if mass transfer from smaller to larger granules is preferred. Granules were also marked with a fluorescent tracer to enable quantification of mass transfer. By using differently sized and shaped granules as starting material, different modes of mass transfer were investigated. Samples were taken after various process durations to investigate the kinetics of the tranfer mechanism. It was found that both small and large granules dispense and receive mass during spheronization. In general, small granules increase their size, while large granules maintain their size or show a slight size decrease, resulting in the particularly narrow monomodal size distribution.

Influence of the surface tension of wet massing liquid on the functionality of microcrystalline cellulose as pelletization aid

This study designed to investigate the impact of surface tension of moistening liquid on the functionality of MCC as pelletization aid. For this purpose, sodium dodecyl sulfate (SDS), poloxamer 188 (PL), di-potassium hydrogen phosphate (K₂HPO₄) and combinations thereof were incorporated into the powder blend comprised of MCC and dicalcium phosphate (DCP) at different levels. Physical mixture (PM) and co-processed composite (Cop) of MCC and sodium carboxymethyl cellulose (SCMC) replaced MCC as pelletization aids. The pellets prepared were characterized for their median diameter (D₅₀), particle size distribution (PSD), sphericity, porosity, tensile strength and disintegration. SDS induced a drop in the surface tension of water from 68.7 to 23.7 mN/m at 0.1% (w/w). In contrast, the surface tension values of PL and K₂HPO₄ solutions were 2.08- and 3.07-fold higher than that of SDS solutions, respectively. MCC based pellets obtained with SDS showed wider PSD and lower sphericity than those made with PL, K₂HPO₄ and their combinations. In addition, the PSD and porosity increased with rise of SDS concentration from 0.05 to 0.25% (w/w). It was thus inferred that a critical surface tension of moistening liquid was essential for functionality of MCC as pelletization aid but not for PM and Cop.

Fibrillated Cellulose via High Pressure Homogenization: Analysis and Application for Orodispersible Films

Powdered cellulose (PC) and microcrystalline cellulose (MCC) are common excipients in pharmaceuticals. Recent investigations imply that particle size is the most critical parameter for the different performance in many processes. High-pressure homogenization (HPH) was used to reduce fiber size of both grades. The effect of the homogenization parameters on suspension viscosity, particle size, and mechanical properties of casted films was investigated. PC suspensions showed higher apparent viscosities and yield stresses under the same process conditions than MCC. SLS reduced shear viscosity and thixotropic behavior of both cellulose grades probably due to increased electrostatic repulsion. Homogenization reduced cellulose particle sizes, but re-agglomeration was too strong to analyze the particle size correctly. MCC films showed a tensile strength of up to 16.0 MPa and PC films up to 4.1 MPa. PC films disintegrated within 30 s whereas MCC films did not. Mixtures of MCC and PC led to more stable films than PC alone, but these films did not disintegrate anymore. Diclofenac sodium was incorporated in therapeutic dose with drug load of 47% into orodispersible PC films. The content uniformity of these films fulfilled requirements of Ph.Eur and the films disintegrated in 12 s. In summary, PC and MCC showed comparable results after HPH and most differences could be explained by the smaller particle size of MCC suspensions. These results confirm the hypothesis that mainly the fiber size during processing is responsible for the existing differences of MCC and PC in pharmaceutical process, e.g., wet-extrusion/spheronization.

Evaluation of ethylcellulose and its pseudolatex (Surelease) in preparation of matrix pellets of theophylline using extrusion-spheronization

OBJECTIVES

This study evaluates the effect of substitution of microcrystalline cellulose (MCC) with ethylcellulose (EC) on mechanical and release characteristics of theophylline pellets.

MATERIALS AND METHODS

The effect of addition of EC was investigated on characteristics of pellets with varying drug content prepared by extrusion-spheronization. Also the effect of type of granulating liquid (water or Surelease) was investigated on characteristics of selected pellets. The pellets were characterized for particle size (sieve analysis), mechanical strength, morphology (microscopy), thermal (DSC) and dissolution behaviors.

RESULTS

The exrtudability of the wet mass was reduced upon inclusion of EC so that complete replacement of MCC was not possible. Increase in EC percentage led to lower production yield and formation of pellets with larger diameter and slightly rough surfaces. Inclusion of EC also affected the mechanical properties of pellets but had negligible effect on drug release profile. The surface of selected pellets became smoother and their production yield increased upon the use of Surelease as granulating liquid. In addition the rate of drug release decreased to some extent when Surelease was used.

CONCLUSION

Preparation of theophylline pellets with EC alone was not possible in process of extrusion-spheronization. Partial replacement of MCC with EC changed physicomechanical properties of pellets but hardly affected drug release. Although the use of Surelease as granulation liquid slightly decreased the rate of drug release, desirable matrix pellets with sustained drug release could not be produced. Despite this outcome however, these pellets could benefit from reduced coating thickness for drug release control.

Approaches to developing fast release pellets via wet extrusion-spheronization

Microcrystalline cellulose (MCC) is widely regarded as the excellent choice to manufacture pellets via wet extrusion-spheronisation (ES) process due to its excellent water uptake capability, water holding capacity, desirable rheological properties, cohesiveness and plasticity etc. Nevertheless, in spite of all these advantages, limitations associated with the application of MCC also have been reported. The most prevailing limitation is prolonged or incomplete drug release profile due to the lack of disintegration as pellet contracts significantly during the drying process, especially when in combination with poorly soluble drug at a high level. This characteristic limits the application of MCC in immediate release formulations. Over the years, many approaches have been tried to overcome this disadvantage, such as modifying MCC, incorporation of superdisintegrant, increasing the porosity of pellet, partial or complete substitution for MCC, enhancing the solubility of poorly soluble drug (e.g. solid dispersion, self-emulsifying drug-delivery system), etc. In this review, we will provide an updated and integrated discussion of current approaches to prepare fast release pellets via wet ES.

Preparation of co-spray dried cushioning agent containing stearic acid for protecting pellet coatings when compressed

This study investigated the applicability of stearic acid as a co-adjuvant in cushioning agent formulated to prevent coat damage when compressing coated pellets. The co-processed and physical blended fillers were prepared by spray drying and physically blending, respectively, with filler ingredients consisting of stearic acid, microcrystalline cellulose, fully gelatinized starch, and corn starch. Pellets containing drug were produced by coating onto non-pariels a drug layer of metformin followed by a sustained-release layer. Drug release from tablets composed of co-processed or physical blended fillers (0, 1, 5, and 10% stearic acid levels) and coated drug containing pellets were analyzed using similarity factor F2. Under the same force and the stearic acid level, co-processed fillers produced pellet containing tablets which showed higher F2 or t50 values and tensile strengths as well as lower yield pressures as compared with tablets containing physical blended fillers. It was shown that the destructive degree of pellet coating was significantly reduced after being co-processed by homogenization and the incorporation of stearic acid in the cushioning agents, as shown by the improved F2 and t50 values. In addition, disintegrate times of tablets containing co-processed agents decreased despite the hydrophobic stearic acid. In conclusion, the inclusion of stearic acid in co-processed cushioning agents was effective at protecting compacted coated pellets from compression-induced damage without compromising disintegratability. The findings could serve as a step towards resolving the technical challenges of balancing the drug release profiles, tablet tensile strength, and disintegration time of compacting coated pellets into multi-particulate-sustained release tablets.