Modified Polymer Matrix in Pharmaceutical Hot Melt Extrusion by Molecular Interactions with a Carboxylic Coformer

Amorphous solid dispersion of a binary formulation with felodipine and HPMC for 3D printed floating tablets

This study focuses on the combination of three-dimensional printing (3DP) and amorphous solid dispersion (ASD) technologies for the manufacturing of gastroretentive floating tablets. Employing hot melt extrusion (HME) and fused deposition modeling (FDM), the study investigates the development of drug-loaded filaments and 3D printed (3DP) tablets containing felodipine as model drug and hydroxypropyl methylcellulose (HPMC) as the polymeric carrier. Prior to fabrication, solubility parameter estimation and molecular dynamics simulations were applied to predict drug-polymer interactions, which are crucial for ASD formation. Physical bulk and surface characterization complemented the quality control of both drug-loaded filaments and 3DP tablets. The analysis confirmed a successful amorphous dispersion of felodipine within the polymeric matrix. Furthermore, the low infill percentage and enclosed design of the 3DP tablet allowed for obtaining low-density systems. This structure resulted in buoyancy during the entire drug release process until a complete dissolution of the 3DP tablets (more than 8 h) was attained. The particular design made it possible for a single polymer to achieve a zero-order controlled release of the drug, which is considered the ideal kinetics for a gastroretentive system. Accordingly, this study can be seen as an advancement in ASD formulation for 3DP technology within pharmaceutics.

Nanostructure and Molecular-Level Characterization of Aminoalkyl Methacrylate Copolymer and the Impact on Drug Solubilization Ability

The effects of pH changes and saccharin (SAC) addition on the nanostructure and mobility of the cationic aminoalkyl methacrylate copolymer Eudragit E PO (EUD-E) and its drug solubilization ability were investigated. Small-angle X-ray scattering performed using synchrotron radiation and atomic force microscopy showed that the EUD-E nanostructure, which has a size of approximately several nanometers, changed from a random coil structure at low pH (pH 4.0-5.0) to a partially folded structure at high pH (pH 5.5-6.5). The EUD-E also formed a partially folded structure in a wide pH range of 4.5-6.5 when SAC was present, and the coil-to-globule transition was moderate with pH increase, compared with that when SAC was absent. The equilibrium solubility of the neutral drug naringenin (NAR) was enhanced in the EUD-E solution and further increased as the pH increased. The enlargement of the hydrophobic region of EUD-E in association with the coil-to-globule transition led to efficient solubilization of NAR. The interaction with SAC enhanced the mobility of the EUD-E chains in the hydrophobic region of EUD-E, resulting in changes in the drug-solubilizing ability. ¹H high-resolution magic-angle spinning NMR measurements revealed that the solubilized NAR in the partially folded structure of EUD-E showed higher molecular mobility in the presence of SAC than in the absence of SAC. This study highlighted that solution pH and the presence of SAC significantly changed the drug solubilization ability of EUD-E, followed by changes in the EUD-E nanostructure, including its hydrophobic region.

Polyelectrolyte Matrices in the Modulation of Intermolecular Electrostatic Interactions for Amorphous Solid Dispersions: A Comprehensive Review

Polyelectrolyte polymers have been widely used in the pharmaceutical field as excipients to facilitate various drug delivery systems. Polyelectrolytes have been used to modulate the electrostatic environment and enhance favorable interactions between the drug and the polymer in amorphous solid dispersions (ASDs) prepared mainly by hot-melt extrusion. Polyelectrolytes have been used alone, or in combination with nonionic polymers as interpolyelectrolyte complexes, or after the addition of small molecular additives. They were found to enhance physical stability by favoring stabilizing intermolecular interactions, as well as to exert an antiplasticizing effect. Moreover, they not only enhance drug dissolution, but they have also been used for maintaining supersaturation, especially in the case of weakly basic drugs that tend to precipitate in the intestine. Additional uses include controlled and/or targeted drug release with enhanced physical stability and ease of preparation via novel continuous processes. Polyelectrolyte matrices, used along with scalable manufacturing methods in accordance with green chemistry principles, emerge as an attractive viable alternative for the preparation of ASDs with improved physical stability and biopharmaceutic performance.

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.

Analytical and Computational Methods for the Determination of Drug-Polymer Solubility and Miscibility

In the pharmaceutical industry, poorly water-soluble drugs require enabling technologies to increase apparent solubility in the biological environment. Amorphous solid dispersion (ASD) has emerged as an attractive strategy that has been used to market more than 20 oral pharmaceutical products. The amorphous form is inherently unstable and exhibits phase separation and crystallization during shelf life storage. Polymers stabilize the amorphous drug by antiplasticization, reducing molecular mobility, reducing chemical potential of drug, and increasing glass transition temperature in ASD. Here, drug-polymer miscibility is an important contributor to the physical stability of ASDs. The current Review discusses the basics of drug-polymer interactions with the major focus on the methods for the evaluation of solubility and miscibility of the drug in the polymer. Methods for the evaluation of drug-polymer solubility and miscibility have been classified as thermal, spectroscopic, microscopic, solid-liquid equilibrium-based, rheological, and computational methods. Thermal methods have been commonly used to determine the solubility of the drug in the polymer, while other methods provide qualitative information about drug-polymer miscibility. Despite advancements, the majority of these methods are still inadequate to provide the value of drug-polymer miscibility at room temperature. There is still a need for methods that can accurately determine drug-polymer miscibility at pharmaceutically relevant temperatures.

The Phospholipid Research Center: Current Research in Phospholipids and Their Use in Drug Delivery

This review summarizes the research on phospholipids and their use for drug delivery related to the Phospholipid Research Center Heidelberg (PRC). The focus is on projects that have been approved by the PRC since 2017 and are currently still ongoing or have recently been completed. The different projects cover all facets of phospholipid research, from basic to applied research, including the use of phospholipids in different administration forms such as liposomes, mixed micelles, emulsions, and extrudates, up to industrial application-oriented research. These projects also include all routes of administration, namely parenteral, oral, and topical. With this review we would like to highlight possible future research directions, including a short introduction into the world of phospholipids.

In Vivo Performance of Innovative Polyelectrolyte Matrices for Hot Melt Extrusion of Amorphous Drug Systems

Hot melt extrusion of amorphous systems has become a pivotal technology to cope with challenges of poorly water-soluble drugs. Previous research showed that small molecular additives with targeted molecular interactions enabled introduction of a polyelectrolyte matrix into hot melt extrusion that would otherwise not be possible to process due to the unfavorable properties upon heating of the pure polymer. Carboxymethyl cellulose sodium (NaCMC) with lysine or alternatively meglumine led to modified polymeric matrices that showed adequate processability by hot melt extrusion and yielded stable amorphous formulations. The investigated formulations, including fenofibrate as a model drug, were characterized by attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry, and viscosity measurements after aqueous dispersion. Further biopharmaceutical assessment started with biorelevant nonsink dissolution testing followed by a pharmacokinetic in vivo study in rats. The in vitro assessment showed superiority of the lysine-containing formulation in the extent of in vitro supersaturation and overall drug release. In accordance with this, the in vivo study also demonstrated increased exposure of the amorphous formulations and in particular for the system containing lysine. In summary, the combination of polyelectrolytes with interacting additives presents a promising opportunity for the formulation of poorly water-soluble drugs.

Successful oral delivery of poorly water-soluble drugs both depends on the intraluminal behavior of drugs and of appropriate advanced drug delivery systems

Poorly water-soluble drugs continue to be a problematic, yet important class of pharmaceutical compounds for treatment of a wide range of diseases. Their prevalence in discovery is still high, and their development is usually limited by our lack of a complete understanding of how the complex chemical, physiological and biochemical processes that occur between administration and absorption individually and together impact on bioavailability. This review defines the challenge presented by these drugs, outlines contemporary strategies to solve this challenge, and consequent in silico and in vitro evaluation of the delivery technologies for poorly water-soluble drugs. The next steps and unmet needs are proposed to present a roadmap for future studies for the field to consider enabling progress in delivery of poorly water-soluble compounds.

An update on the contribution of hot-melt extrusion technology to novel drug delivery in the twenty-first century: part II

INTRODUCTION

Interest in hot-melt extrusion (HME) technology for novel applications is growing day by day, which is evident from several hundred publications within the last 5 years. HME is a cost-effective, solvent free, 'green' technology utilized for various formulations with low investment costs compared to conventional technologies. HME has also earned the attention of the pharmaceutical industry by the transformation of this technology for application in continuous manufacturing.

AREAS COVERED

Part II of the review focuses on various novel opportunities or innovations of HME such as multiple component systems (co-crystals, co-amorphous systems and salts), twin-screw granulation, semi-solids, co-extrusion, abuse deterrent formulations, solid self-emulsifying drug delivery systems, chronotherapeutic drug delivery systems, and miscellaneous applications.

EXPERT OPINION

HME is being investigated as an alternative technology for preparation of multicomponent systems such as co-crystals and co-amorphous techniques. Twin-screw granulation has gained increased interest in preparation of granules via twin-screw melt granulation or twin-screw dry granulation. This novel application of the HME process provides a promising alternate approach in the formulation of granules and solid dosage forms. However, this technology may need to be further investigated for scalability aspects of these novel applications for industrial production.

Polyelectrolytes in Hot Melt Extrusion: A Combined Solvent-Based and Interacting Additive Technique for Solid Dispersions

Solid dispersions are important supersaturating formulations to orally deliver poorly water-soluble drugs. A most important process technique is hot melt extrusion but process requirements limit the choice of suitable polymers. One way around this limitation is to synthesize new polymers. However, their disadvantage is that they require toxicological qualification and present regulatory hurdles for their market authorization. Therefore, this study follows an alternative approach, where new polymeric matrices are created by combining a known polymer, small molecular additives, and an initial solvent-based process step. The polyelectrolyte, carboxymethylcellulose sodium (NaCMC), was tested in combination with different additives such as amino acids, meglumine, trometamol, and urea. It was possible to obtain a new polyelectrolyte matrix that was viable for manufacturing by hot melt extrusion. The amount of additives had to be carefully tuned to obtain an amorphous polymer matrix. This was achieved by probing the matrix using several analytical techniques, such as Fourier transform infrared spectroscopy, differential scanning calorimetry, hot stage microscopy, and X-ray powder diffraction. Next, the obtained matrices had to be examined to ensure the homogeneous distribution of the components and the possible residual crystallinity. As this analysis requires probing a sample on several points and relies on high quality data, X-ray diffraction and starring techniques at a synchrotron source had to be used. Particularly promising with NaCMC was the addition of lysine as well as meglumine. Further research is needed to harness the novel matrix with drugs in amorphous formulations.