Hot Melt Extrusion: Development of an Amorphous Solid Dispersion for an Insoluble Drug from Mini-scale to Clinical Scale

The objective of the study was to develop an amorphous solid dispersion (ASD) for an insoluble compound X by hot melt extrusion (HME) process. The focus was to identify material-sparing approaches to develop bioavailable and stable ASD including scale up of HME process using minimal drug. Mixtures of compound X and polymers with and without surfactants or pH modifiers were evaluated by hot stage microscopy (HSM), polarized light microscopy (PLM), and modulated differential scanning calorimetry (mDSC), which enabled systematic selection of ASD components. Formulation blends of compound X with PVP K12 and PVP VA64 polymers were extruded through a 9-mm twin screw mini-extruder. Physical characterization of extrudates by PLM, XRPD, and mDSC indicated formation of single-phase ASD's. Accelerated stability testing was performed that allowed rapid selection of stable ASD's and suitable packaging configurations. Dissolution testing by a discriminating two-step non-sink dissolution method showed 70-80% drug release from prototype ASD's, which was around twofold higher compared to crystalline tablet formulations. The in vivo pharmacokinetic study in dogs showed that bioavailability from ASD of compound X with PVP VA64 was four times higher compared to crystalline tablet formulations. The HME process was scaled up from lab scale to clinical scale using volumetric scale up approach and scale-independent-specific energy parameter. The present study demonstrated systematic development of ASD dosage form and scale up of HME process to clinical scale using minimal drug (∼500 g), which allowed successful clinical batch manufacture of enabled formulation within 7 months.

Characterization and performance assessment of solid dispersions prepared by hot melt extrusion and spray drying process

The present study investigated effect of manufacturing methods such as hot melt extrusion (HME) and spray drying (SD) on physicochemical properties, manufacturability, physical stability and product performance of solid dispersion. Solid dispersions of compound X and PVP VA64 (1:2) when prepared by SD and HME process were amorphous by polarized light microscopy, powder X-ray diffractometry, and modulated differential scanning calorimetry analyses with a single glass transition temperature. Fourier transform infrared (FT-IR) and Raman spectroscopic analyses revealed similar molecular level interactions between compound X and PVP VA64 as evident by overlapping FT-IR and FT Raman spectra in SD and HME solid dispersions. The compactibility, tabletability, disintegration and dissolution performance were similar for solid dispersions prepared by both processing techniques. Differences in material properties such as surface area, morphological structure, powder densities, and flow characteristics were observed between SD and HME solid dispersion. The SD solid dispersion was physically less stable compared to HME solid dispersion under accelerated stability conditions. Findings from this study suggest that similar product performance could be obtained if the molecular properties of the solid dispersion processed by two different techniques are similar. However differences in material properties might affect the physical stability of the solid dispersions.

Water Distribution Studies Within Microcrystalline Cellulose and Chitosan using Differential Scanning Calorimetry and Dynamic Vapor Sorption Analysis

The objective of the study was to assess and compare the interaction and distribution of water within microcrystalline cellulose (MCC) and chitosan by differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water in hydrated samples were determined from melting endotherms obtained by DSC. After accounting for the percent crystallinity of MCC and chitosan, no statistically significant difference was observed in their ability to bind water molecules per repeating unit at the minimum water content at which freezing water is evident. Exposure of chitosan to water for 30 min was sufficient to achieve equilibration at 61% w/w actual water content. The moisture sorption profiles were analyzed according to the GAB and Young and Nelson equations. The adsorbed monolayer, externally adsorbed moisture, and internally absorbed moisture were not statistically different for MCC and chitosan after accounting for the amorphous content of the polymers. These studies suggest that chitosan can act as a "molecular sponge," and thus aid in the production of beads by extrusion and spheronization.

Extruded and Spheronized Beads Containing No Microcrystalline Cellulose: Influence of Formulation and Process Variables

The purposes of this study were to investigate the use of chitosan in the manufacture of beads by extrusion-spheronization without inclusion of microcrystalline cellulose, and to study the effect of formulation and process variables on the characteristics of the beads. Beads containing chitosan, fine particle ethylcellulose, hydroxypropyl methylcellulose (HPMC), and caffeine as the model drug were manufactured. Bead size, yield, shape, friability, density, porosity, and release studies were determined. Spherical beads with good mechanical properties could be manufactured without microcrystalline cellulose. Release studies showed that there was immediate release of drug from the beads. A five factor, half fraction screening design was employed to study the effect of formulation variables and process variables on the properties of the beads. Statistical analysis indicated that formulation variables such as the chitosan content, HPMC content, and water content, and process variables such as the spheronizer speed and extruder speed significantly affected the physical properties of the beads. The bead size decreased with an increase in chitosan content. Significant two-factor interactions exist between the variables for several of the measured responses. Beads with high percentage yield and high sphericity can be obtained at high chitosan content, and low HPMC content, water content, spheronizer speed, and extruder speed. Less friable beads can be obtained at high levels of studied formulation variables and low levels of studied process variables. Beads of high density and low porosity can be manufactured at high levels of the studied formulation and process variables. Regression equations were generated using Statgraphics Plus software that can be used to develop formulations with desired bead properties. Chitosan was useful to provide beads of acceptable physical properties using water as a granulating fluid in the extrusion-spheronization process.

Studies on the interaction of water with ethylcellulose: effect of polymer particle size

The purpose of this research was to investigate the interaction of water with ethylcellulose samples and assess the effect of particle size on the interaction. The distribution of water within coarse particle ethylcellulose (CPEC; average particle size 310 micro m) and fine particle ethylcellulose (FPEC; average particle size 9.7 micro m) of 7 cps viscosity grade was assessed by differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water in hydrated samples were determined from melting endotherms obtained by DSC. An increase in water content resulted in an increase in the enthalpy of fusion of water for the two particle size fractions of EC. The amount of nonfreezable water was not affected by the change in particle size at low water contents. Exposure of ethylcellulose to water for 30 minutes is sufficient to achieve equilibration within the hydrated polymer at 47% wt/wt water content. The moisture sorption profiles were analyzed according to the Guggenheim-Anderson-de Boer (GAB) and Young and Nelson equations, which can help to distinguish moisture distribution in different physical forms. The amount of externally adsorbed moisture was greater in the case of FPEC. Internally absorbed moisture was evident only with the CPEC. In light of these results, an explanation is offered for the success of FPEC in wet-granulation methods where CPEC was not successful.

Wet granulation fine particle ethylcellulose tablets: effect of production variables and mathematical modeling of drug release

In the present study, the applicability of fine particle ethylcellulose (FPEC) to produce matrix tablets by a wet granulation technique was evaluated. The effect of various formulation and process variables, such as FPEC content, hardness of the tablet, and solubility of the drug, on the release of drug from these tablets was examined. Tablets were prepared by wet granulation of drug and FPEC in an appropriate mass ratio. Theophylline, caffeine, and dyphylline were selected as nonionizable model drugs with solubilities from 8.3 to 330 mg/mL at 25 degrees C. Ibuprofen, phenylpropanolamine hydrochloride, and pseudoephedrine hydrochloride were selected as ionizable drugs with solubilities from 0.1 to 2000 mg/mL at 25 degrees C. Drug release studies were conducted in 37 degrees C water with UV detection. As the FPEC content and the hardness of the tablets increased, the release rate of the drug decreased. The drug release rate increased with an increase in the solubility of the drug. Model equations, intended to elucidate the drug release mechanism, were fitted to the release data. Parameters were generated and data presented by SAS software. The Akaike Information Criterion was also considered to ascertain the best-fit equation. Fickian diffusion and polymer relaxation were the release mechanisms for nonionizable and ionizable drugs.