Investigation of the interactions of enteric and hydrophilic polymers to enhance dissolution of griseofulvin following hot melt extrusion processing

Assessing processability of milled HME extrudates: Consolidating the effect of extrusion temperature, drug loading, and particle size via Non-dimensional cohesion

The downstream processability of Hot Melt Extrusion (HME) Amorphous Solid Dispersions (ASD), an underexplored topic of importance, was assessed through a multi-faceted particle engineering approach. Extrudates, comprised of griseofulvin (GF), a model poorly water-soluble drug, and hydroxypropyl cellulose (HPC), were prepared at four drug concentrations and three HME temperature profiles to yield cases with and without residual crystallinity and subsequently milled to five sieve cuts ranging from < 45 μm to 355 - 500 μm. Solid state characterization was performed with XRPD, FT-IR, and TGA. Particle scale properties of the milled extrudates were evaluated including particle size, density, surface energy, and morphologies imaged via SEM. It was observed that regardless of sieve cut size, drug concentration and HME conditions impacted the flowability trends, quantified via Flow Function Coefficient (FFC) and bulk density. As a novelty, the effects of various process parameters and drug loadings were consolidated into a dimensionless interparticle cohesion measure, granular Bond Number (Bog), to better correlate them with bulk powder properties. The significant contrast in particle morphologies, particle size, and densities among selected cases demonstrated that particle size alone should not be the sole consideration when correlating particle scale to bulk powder scale properties of milled extrudates. Instead, the HME temperature profile and ASD drug loading may be more suitable parameters affecting the bulk powder properties of the milled extrudates.

QbD-Based Development and Evaluation of Pazopanib Hydrochloride Extrudates Prepared by Hot-Melt Extrusion Technique: In Vitro and In Vivo Evaluation

BACKGROUND

Pazopanib hydrochloride (PZB) is a protein kinase inhibitor approved by the United States Food and Drug Administration and European agencies for the treatment of renal cell carcinoma and other renal malignancies. However, it exhibits poor aqueous solubility and inconsistent oral drug absorption. In this regard, the current research work entails the development and evaluation of the extrudates of pazopanib hydrochloride by the hot-melt extrusion (HME) technique for solubility enhancement and augmenting oral bioavailability.

RESULTS

Solid dispersion of the drug was prepared using polymers such as Kollidon VA64, hydroxypropylmethylcellulose (HPMC), Eudragit EPO, and Affinisol 15LV in a 1:2 ratio by the HME process through a lab-scale 18 mm extruder. Systematic optimization of the formulation variables was carried out with the help of custom screening design (JMP Software by SAS, Version 14.0) to study the impact of polymer type and plasticizer level on the quality of extrudate processability by measuring the torque value, appearance, and disintegration time as the responses. The polymer blends containing Kollidon VA64 and Affinisol 15LV resulted in respective clear transparent extrudates, while Eudragit EPO and HPMC extrudates were found to be opaque white and brownish, respectively. Furthermore, evaluation of the impact of process parameters such as screw rpm and barrel temperature was measured using a definitive screening design on the extrude appearance, torque, disintegration time, and dissolution profile. Based on the statistical outcomes, it can be concluded that barrel temperature has a significant impact on torque, disintegration time, and dissolution at 30 min, while screw speed has an insignificant impact on the response variables. Affinisol extrudates showed less moisture uptake and faster dissolution in comparison to Kollidon VA64 extrudates. Affinisol extrudates were evaluated for polymorphic stability up to a 3-month accelerated condition and found no recrystallization. PZB-Extrudates using the Affinisol polymer (Test formulation A) revealed significantly higher bioavailability (AUC) in comparison to the free Pazopanib drug and marketed formulation.

The step-wise dissolution method: An efficient DSC-based protocol for verification of predicted API-polymer compatibility

The development of an amorphous solid dispersion (ASD) is a promising strategy for improving the low bioavailability of many poorly water-soluble active pharmaceutical ingredients (APIs). The construction of a temperature-composition (T-C) phase diagram for an API-polymer combination is imperative as it can provide critical information that is essential for formulating stable ASDs. However, the currently followed differential scanning calorimetry (DSC)-based strategies for API solubility determination in a polymer at elevated temperatures are inefficient and, on occasions, unreliable, which may lead to an inaccurate prediction at lower temperatures of interest (i.e., T = 25 °C). Recently, we proposed a novel DSC-based protocol called the "step-wise dissolution" (S-WD) method, which is both cost- and time-effective. The objective of this study was to test the applicability of the S-WD method regarding expeditious verification of the purely-predicted API-polymer compatibility via the perturbed chain-statistical associating fluid theory (PC-SAFT) equation of state (EOS). Fifteen API-polymer T-C phase diagrams were reliably constructed, with three distinct API-polymer case types being identified regarding the approach used for the S-WD method. Overall, the PC-SAFT EOS provided satisfactory qualitative descriptions of the API-polymer compatibility, but not necessarily accurate quantitative predictions of the API solubility in the polymer at T = 25 °C. The S-WD method was subsequently modified and an optimal protocol was proposed, which can significantly reduce the required experimental effort.

Thermal degradation of Affinisol HPMC: Optimum Processing Temperatures for Hot Melt Extrusion and 3D Printing

PURPOSE

Affinisol HPMC HME is a new popular form of hypromellose specifically designed for the hot melt extrusion and 3D printing of pharmaceutical products. However, reports of its thermal stability include only data obtained under inert N2 atmosphere, which is not consistent with the common pharmaceutical practice. Therefore, detailed investigation of its real-life thermal stability in air is paramount for identification of potential risks and limitations during its high-temperature processing.

METHODS

In this work, the Affinisol HPMC HME 15LV powder as well as extruded filaments will be investigated by means of thermogravimetry, differential scanning calorimetry and infrared spectroscopy with respect to its thermal stability.

RESULTS

The decomposition in N2 was proceeded in accordance with the literature data and manufacturer's specifications: onset at ~260°C at 0.5°C·min-1, single-step mass loss of 90-95%. However, in laboratory or industrial practice, high-temperature processing is performed in the air, where oxidation-induced degradation drastically changes. The thermogravimetric mass loss in air proceeded in three stages: ~ 5% mass loss with onset at 150°C, ~ 70% mass loss at 200°C, and ~ 15% mass loss at 380°C. Diffusion of O2 into the Affinisol material was identified as the rate-determining step.

CONCLUSION

For extrusion temperatures ≥170°C, Affinisol exhibits a significant degree of degradation within the 5 min extruder retention time. Hot melt extrusion of pure Affinisol can be comfortably performed below this temperature. Utilization of plasticizers may be necessary for safe 3D printing.

A Review on Physicochemical Properties of Polymers Used as Filaments in 3D-Printed Tablets

Three-dimensional (3D) printing technology has presently been explored widely in the field of pharmaceutical research to produce various conventional as well as novel dosage forms such as tablets, capsules, oral films, pellets, subcutaneous implants, scaffolds, and vaginal rings. The use of this innovative method is a good choice for its advanced technologies and the ability to make tailored medicine specifically for individual patient. There are many 3D printing systems that are used to print tablets, implants, and vaginal rings. Among the available systems, the fused deposition modeling (FDM) is widely utilized. The FDM has been regarded as the best choice of printer as it shows high potential in the production of tablets as a unit dose in 3D printing medicine manufacturing. In order to design a 3D-printed tablet or other dosage forms, the physicochemical properties of polymers play a vital role. One should have proper knowledge about the polymer's properties so that one can select appropriate polymers in order to design 3D-printed dosage form. This review highlighted the various physicochemical properties of polymers that are currently used as filaments in 3D printing. In this manuscript, the authors also discussed various systems that are currently adopted in the 3D printing.

Enteric and hydrophilic polymers enhance dissolution and absorption of poorly soluble acidic drugs based on micro-environmental pH-modifying solid dispersion

The oral bioavailability of poorly water-soluble active pharmaceutical ingredient (API) is often inadequate for the desired therapeutic effect. Micro-environmental pH-modifying solid dispersion (micro pHm SD) is an effective method for enhancing the dissolution of pH-dependent soluble APIs. However, erratic bioavailability of these drugs was often found when the micro pHm SD of the drugs was orally administrated and passed through the gastrointestinal tract. Because the added alkalizer in micro pHm SD could be neutralized by the acid in the stomach, as a result not enough alkalizer is left to form alkaline micro-environment around the drug in the intestine, leading to poor dissolution and bioavailability of API. Enteric polymers are applicable materials for site-specific drug delivery that are insoluble in gastric tract but soluble in the intestine targeted for drug release. In this study, a poorly water-soluble model drug, toltrazuril (TOL), was prepared as enteric micro pHm SD with enteric, hydrophilic polymers and alkalizer. The surface of enteric micro pHm SD tablets staining and alkalizer protection test in the acid dissolution medium qualitatively and quantitatively confirmed the protective effects of the enteric polymer on the alkalizer. Dissolution studies revealed that the drug release from the enteric micro pHm SDs was improved significantly compared with micro pHm SD with no enteric polymer. The pH-dependent solubility of enteric polymer had effects on the dissolution of APIs from the SDs in neutral medium. Enteric micro pHm SDs with higher proportion of enteric polymer showed higher C_max and dissolution rate of TOL. The physicochemical characterization and the molecular interaction between drug and matrix were analyzed by electron microscopy (SEM), differential scanning calorimetry (DSC), and fourier transform infrared spectroscopy (FTIR), finding that the formation of hydrogen bonds between TOL and matrix was helpful to promote dissolution of TOL. Ca(OH)₂-TOL-PVPk30-HPMCAS 8: 8: 18: 6 was determined as the most optimal enteric micro pHm SD, which significantly improved the bioavailability of TOL and its active metabolism (TOLSO, TOLSO₂) in pharmacokinetic study and could effectively reduce the irritation of the gastrointestinal mucosa caused by the alkalizer Ca(OH)₂ when the SD was orally administrated to rabbits. The present study demonstrates that formulating APIs with poor water solubility as enteric micro pHm SD is an effective method for protecting the alkalizer in SD and improving the dissolution of APIs and the bioavailability following oral administration.

Recent Trends in Assessment of Cellulose Derivatives in Designing Novel and Nanoparticulate-Based Drug Delivery Systems for Improvement of Oral Health

Natural polymers are revolutionizing current pharmaceutical dosage forms design as excipient and gained huge importance because of significant influence in formulation development and drug delivery. Oral health refers to the health of the teeth, gums, and the entire oral-facial system that allows us to smile, speak, and chew. Since years, biopolymers stand out due to their biocompatibility, biodegradability, low toxicity, and stability. Polysaccharides such as cellulose and their derivatives possess properties like novel mechanical robustness and hydrophilicity that can be easily fabricated into controlled-release dosage forms. Cellulose attracts the dosage design attention because of constant drug release rate from the precursor nanoparticles. This review discusses the origin, extraction, preparation of cellulose derivatives and their use in formulation development of nanoparticles having multidisciplinary applications as pharmaceutical excipient and in drug delivery, as bacterial and plant cellulose have great potential for application in the biomedical area, including dentistry, protein and peptide delivery, colorectal cancer treatment, and in 3D printable dosage forms.

Enhanced Supersaturation via Fusion-Assisted Amorphization during FDM 3D Printing of Crystalline Poorly Soluble Drug Loaded Filaments

Filaments loaded with griseofulvin (GF), a model poorly water-soluble drug, were prepared and used for 3D printing via fused deposition modeling (FDM). GF was selected due to its high melting temperature, enabling lower temperature hot-melt extrusion (HME) keeping GF largely crystalline in the filaments, which could help mitigate the disadvantages of high HME processing temperatures such as filament quality, important for printability and the adverse effects of GF recrystallization on tablet properties. Novel aspects include single-step fusion-assisted ASDs generation during FDM 3D printing and examining the impact of tablet surface areas (SA) through printing multi-mini and square-pattern perforated tablets to further enhance drug supersaturation during dissolution. Kollicoat protect and hydroxypropyl cellulose were selected due to their low miscibility with GF, necessary to produce crystalline filaments. The drug solid-state was assessed via XRPD, DSC and FT-IR. At 165 °C HME processing temperature, the filaments containing ~80% crystalline GF were printable. Fusion-assisted 3D printing led to GF supersaturation of ~153% for cylindrical tablets and ~293% with the square-pattern perforated tablets, indicating strong monotonous impact of tablet SA. Dissolution kinetics of drug release profiles indicated Fickian transport for tablets with higher SA, demonstrating greater SA-induced drug supersaturation for well-designed 3D printed tablets.

Eudragit®: A Versatile Family of Polymers for Hot Melt Extrusion and 3D Printing Processes in Pharmaceutics

Eudragit® polymers are polymethacrylates highly used in pharmaceutics for the development of modified drug delivery systems. They are widely known due to their versatility with regards to chemical composition, solubility, and swelling properties. Moreover, Eudragit polymers are thermoplastic, and their use has been boosted in some production processes, such as hot melt extrusion (HME) and fused deposition modelling 3D printing, among other 3D printing techniques. Therefore, this review covers the studies using Eudragit polymers in the development of drug delivery systems produced by HME and 3D printing techniques over the last 10 years. Eudragit E has been the most used among them, mostly to formulate immediate release systems or as a taste-masker agent. On the other hand, Eudragit RS and Eudragit L100-55 have mainly been used to produce controlled and delayed release systems, respectively. The use of Eudragit polymers in these processes has frequently been devoted to producing solid dispersions and/or to prepare filaments to be 3D printed in different dosage forms. In this review, we highlight the countless possibilities offered by Eudragit polymers in HME and 3D printing, whether alone or in blends, discussing their prominence in the development of innovative modified drug release systems.

Investigation of the Dependence of the Flory-Huggins Interaction Parameter on Temperature and Composition in a Drug-Polymer System

The Flory-Huggins (F-H) solubility equation has been widely used to describe the solubility of a small-molecule drug in a polymeric carrier and thus determine the design space available for formulating a stable amorphous solid dispersion. The F-H interaction parameter (χ) describes the thermodynamic properties of drug-polymer solutions and accounts for any enthalpic and entropic changes in solubility. Many studies have found that for a limited compositional range, χ varies proportionally to the inverse of the melting temperature of the drug. We explored this relationship using a highly sensitive DSC technique to detect remaining residual crystalline active pharmaceutical ingredients (APIs) following annealing of ball milled mixtures of crystalline itraconazole (ITZ) and either Soluplus or hydroxypropyl methylcellulose phthalate (HPMCP) at temperatures near the estimated solubility curve. Depending on the experimental approach taken, the measurement of drug-polymer solubility can be restricted to mixtures with a high proportion of drug, but in this study, solubility was experimentally determined for mixtures with API content as low as 10 wt %. Results suggest that the proposed linear relationship does not extend to compositions with smaller amounts of API, instead indicating that χ was both temperature- and composition-dependent for the systems studied. The feasibility of this technique to measure interactions in a ternary system containing itraconazole and both polymers was also determined; ITZ-HPMCP exhibited the most favorable values of χ, while ITZ-Soluplus and ITZ-Soluplus-HPMCP demonstrated similar interaction parameters.

Melt Extrusion for a High Melting Point Compound with Improved Solubility and Sustained Release

The objective of the current study was to develop an amorphous solid dispersion for a high melting point compound, griseofulvin (GRF), with an enhanced solubility and a controlled release pattern utilizing hot melt extrusion (HME) technology. Hypromellose acetate succinate (HPMCAS, Shin-Etsu AQOAT®, medium particle size) was explored as the polymeric carrier, while hypromellose (HPMC, Metolose® SR) was chosen as the release rate control agent. GRF presented an HPMCAS grade-dependent solubility: AS-HMP > AS-MMP > AS-LMP. At 10 wt.% loading, the release of GRF was prolonged to 6 h with the incorporation of 10% HPMC 90SH-100SR, while its solubility was enhanced up to sevenfold. Fourier transform infrared spectroscopy (FT-IR) identified the H-bonding between drug and polymers. Element analysis utilizing X-ray photoelectron spectroscopy (XPS) discovered that less GRF aggregated on the surface of binary powders compared with ternary powders containing HPMC, indicating the relatively poor wettability of the latter one. The morphology of extrudates was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), illustrating a much smoother and uniform surface of binary extrudates. Immediate release tablets including 10% super-disintegrant L-HPC were able to achieve identical dissolution profile as the powders of extrudates.

The Need for Restructuring the Disordered Science of Amorphous Drug Formulations

The alarming numbers of poorly soluble discovery compounds have centered the efforts towards finding strategies to improve the solubility. One of the attractive approaches to enhance solubility is via amorphization despite the stability issue associated with it. Although the number of amorphous-based research reports has increased tremendously after year 2000, little is known on the current research practice in designing amorphous formulation and how it has changed after the concept of solid dispersion was first introduced decades ago. In this review we try to answer the following questions: What model compounds and excipients have been used in amorphous-based research? How were these two components selected and prepared? What methods have been used to assess the performance of amorphous formulation? What methodology have evolved and/or been standardized since amorphous-based formulation was first introduced and to what extent have we embraced on new methods? Is the extent of research mirrored in the number of marketed amorphous drug products? We have summarized the history and evolution of amorphous formulation and discuss the current status of amorphous formulation-related research practice. We also explore the potential uses of old experimental methods and how they can be used in tandem with computational tools in designing amorphous formulation more efficiently than the traditional trial-and-error approach.

A New Extrudable Form of Hypromellose: AFFINISOL™ HPMC HME

Hypromellose is a hydrophilic polymer widely used in immediate- and modified-release oral pharmaceutical dosage forms. However, currently available grades of hypromellose are difficult, if not impossible, to process by hot melt extrusion (HME) because of their high glass transition temperature, high melt viscosity, and low degradation temperature. To overcome these challenges, a modified grade of hypromellose, AFFINISOL™ HPMC HME, was recently introduced. It has a significantly lower glass transition temperature and melt viscosity as compared to other available grades of hypromellose. The objective of this paper is to assess the extrudability and performance of AFFINISOL™ HPMC HME (100LV and 4M) as compared to other widely used polymers in HME, including HPMC 2910 100cP (the currently available hypromellose), Soluplus®, Kollidon® VA 64, and EUDRAGIT® E PO. Formulations containing polymer and carbamazepine (CBZ) were extruded on a co-rotating 16-mm twin-screw extruder, and the effect of temperature, screw speed, and feed rate was investigated. The performance of the solid dispersions was evaluated based on Flory-Huggins modeling and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and dissolution. All formulations extruded well except for HPMC 2910 100cP, which resulted in over-torqueing the extruder (machine overloading because the motor cannot provide efficient energy to rotate the shaft). Among the HME extrudates, only the EUDRAGIT® E PO formulation was crystalline as confirmed by DSC, XRD, and Raman, which agreed with predictions from Flory-Huggins modeling. Dissolution testing was conducted under both sink and non-sink conditions. Sink dissolution testing in neutral media revealed that amorphous CBZ in the HME extrudates completely dissolved within 15 min, which was much more rapid than the time for complete dissolution of bulk CBZ (60 min) and EUDRAGIT® E PO solid dispersion (more than 6 h). Non-sink dissolution in acidic media testing revealed that only CBZ contained in the AFFINISOL™ HPMC HME, and EUDRAGIT® E PO solid dispersions rapidly supersaturated after 15 min, reaching a twofold drug concentration compared to the CBZ equilibrium solubility. In summary, AFFINISOL™ HPMC HME 100LV and AFFINISOL™ HPMC HME 4M are useful in the pharmaceutical HME process to increase wetting and dissolution properties of poorly water-soluble drugs like CBZ.