Process analytical techniques for hot-melt extrusion and their application to amorphous solid dispersions

In-line monitoring of solid dispersion preparation in small scale extrusion based on UV-vis spectroscopy

The poor solubility of a large number of active pharmaceutical ingredients (APIs) is a major challenge in pharmaceutical research. Therefore, the extrusion of amorphous solid dispersions (ASDs) is one promising approach to enhance the dissolution rate by molecularly dissolving the API in an amorphous carrier polymer. During ASD extrusion, crucial parameters as the dissolution of the API in the carrier polymer need to be monitored. Within this study, a small scale twin screw extruder was coupled with special ColVisTec UV-vis probes that are characterized by their small dimensions. This setup enables a systematic formulation design and optimization based on in-line monitoring of drug dissolution using small material quantities. In fact, sample quantities of about 5 mg were evaluated for each measurement, representing 50% of the material inside the die. The amount of undissolved drug particles was determined based on the lightness of the extrudates. It was shown that the temperature has a significant effect on the drug dissolution in the polymer. Furthermore, complete drug dissolution was shifted to lower temperatures if higher residence times were applied. Based on the courses of lightness, regime maps were modeled that specify the process conditions where ASDs are successfully manufactured.

Tailored Supersaturable Immediate Release Behaviors of Hypotensive Supersaturating Drug-Delivery Systems Combined with Hot-Melt Extrusion Technique and Self-Micellizing Polymer

The short-term immediate release of supersaturated drug-delivery systems (SDDSs) presents an interesting process that can be tailored to multi-stage release events including initial release after dosing and dissolution, evolved release over longer dissolution periods for biological absorption, and terminal release following the end of immediate release. However, although comprehensive analysis of these critical release behaviors is often ignored yet essential for understanding the supersaturable immediate-release events for supersaturable solid formations when employing new techniques or polymers matched to a particular API. Hot-melt extrusion (HME) has become a popular continuous thermodynamic disordering technique for amorphization. The self-micellizing polymer Soluplus^® is reported to be a potential amorphous and amphiphilic graft copolymer frequently used in many nano/micro supersaturable formulations. Our current work aims to develop hypotensive supersaturating solid dispersion systems (faSDDS_HME) containing the BCS II drug, felodipine, when coordinately employing the HME technique and self-micellizing Soluplus^®, and to characterize their amorphization as well as immediate release. Other discontinuous techniques were used to prepare control groups (faSDDS_SE and faSDDS_QC). Tailored initial/evolved/terminal three-stage supersaturable immediate-release behaviors were identified and possible mechanisms controlling the release were explored. HME produced the highest initial release in related faSDDS_HME. During the evolved-release period, highly extended "spring-parachute" process was found in HME-induced amorphization owing to its superior supersaturation duration. Due to the enhanced crystallization inhibition effect, faSDDS_HME displayed the strongest terminal release as measured by solubility. For release mechanisms associated with HME, molecular interaction is not the likely dominant mechanism responsible for the improved properties induced by faSDDS_HME. For release mechanisms involved with the polymer Soluplus^® itself, they were found to inhibit drug recrystallization, spontaneously solubilize the drug and lead to improved molecular interactions in all SDDS systems, which were the factors responsible for the improved release. These mechanisms play an important role for the generation of an extended multi-stage immediate release produced via HME or self-micellizing polymer. This study provides a deeper understanding on amorphization and superior multi-stage supersaturable immediate-release behaviors for a particular hypotensive supersaturated delivery system combined with an HME-based continuous manufacturing technique and self-micellizing polymer strategy.

NIR Spectroscopy as an Online PAT Tool for a Narrow Therapeutic Index Drug: Toward a Platform Approach Across Lab and Pilot Scales for Development of a Powder Blending Monitoring Method and Endpoint Determination

An online near-infrared (NIR) spectroscopy platform system for real-time powder blending monitoring and blend endpoint determination was tested for a phenytoin sodium formulation. The study utilized robust experimental design and multiple sensors to investigate multivariate data acquisition, model development, and model scale-up from lab to manufacturing. The impact of the selection of various blend endpoint algorithms on predicted blend endpoint (i.e., mixing time) was explored. Spectral data collected at two process scales using two NIR spectrometers was incorporated in a single (global) calibration model. Unique endpoints were obtained with different algorithms based on standard deviation, average, and distributions of concentration prediction for major components of the formulation. Control over phenytoin sodium's distribution was considered critical due to its narrow therapeutic index nature. It was found that algorithms sensitive to deviation from target concentration offered the simplest interpretation and consistent trends. In contrast, algorithms sensitive to global homogeneity of active and excipients yielded the longest mixing time to achieve blending endpoint. However, they were potentially more sensitive to subtle uniformity variations. Qualitative algorithms using principal component analysis (PCA) of spectral data yielded the prediction of shortest mixing time for blending endpoint. The hybrid approach of combining NIR data from different scales presents several advantages. It enables simplifying the chemometrics model building process and reduces the cost of model building compared to the approach of using data solely from commercial scale. Success of such a hybrid approach depends on the spectroscopic variability captured at different scales and their relative contributions in the final NIR model.

A systematic and robust assessment of hot-melt extrusion-based amorphous solid dispersions: Theoretical prediction to practical implementation

Amorphous solid dispersions (ASDs) have gained attention as a formulation strategy in recent years, with the potential to improve the apparent solubility and, hence, the oral bioavailability of poorly soluble drugs. The process of formulating ASDs is commonly faced with challenges owing to the intrinsic physical and chemical instability of the initial amorphous form and the long-term physical stability of drug formulations. Numerous research publications on hot-melt extrusion (HME) technology have demonstrated that it is the most efficient approach for manufacturing reasonably stable ASDs. The HME technique has been established as a faster scale-up production strategy for formulation evaluation and has the potential to minimize the time to market. Thermodynamic evaluation and theoretical predictions of drug-polymer solubility and miscibility may assist to reduce the product development cost by HME. This review article highlights robust and established prediction theories and experimental approaches for the selection of polymeric carriers for the development of hot melt extrusion based stable amorphous solid dispersions (ASDs). In addition, this review makes a significant contribution to the literature as a pilot guide for ASD assessment, as well as to confirm the drug-polymer compatibility and physical stability of HME-based formulations.

Metamorphosis of Twin Screw Extruder-Based Granulation Technology: Applications Focusing on Its Impact on Conventional Granulation Technology

In order to be at pace with the market requirements of solid dosage forms and regulatory standards, a transformation towards systematic processing using continuous manufacturing (CM) and automated model-based control is being thought through for its fundamental advantages over conventional batch manufacturing. CM eliminates the key gaps through the integration of various processes while preserving quality attributes via the use of process analytical technology (PAT). The twin screw extruder (TSE) is one such equipment adopted by the pharmaceutical industry as a substitute for the traditional batch granulation process. Various types of granulation techniques using twin screw extrusion technology have been explored in the article. Furthermore, individual components of a TSE and their conjugation with PAT tools and the advancements and applications in the field of nutraceuticals and nanotechnology have also been discussed. Thus, the future of granulation lies on the shoulders of continuous TSE, where it can be coupled with computational mathematical studies to mitigate its complications.

Polymers in pharmaceutical additive manufacturing: A balancing act between printability and product performance

Materials and manufacturing processes share a common purpose of enabling the pharmaceutical product to perform as intended. This review on the role of polymeric materials in additive manufacturing of oral dosage forms, focuses on the interface between the polymer and key stages of the additive manufacturing process, which determine printability. By systematically clarifying and comparing polymer functional roles and properties for a variety of AM technologies, together with current and emerging techniques to characterize these properties, suggestions are provided to stimulate the use of readily available and sometimes underutilized pharmaceutical polymers in additive manufacturing. We point to emerging characterization techniques and digital tools, which can be harnessed to manage existing trade-offs between the role of polymers in printer compatibility versus product performance. In a rapidly evolving technological space, this serves to trigger the continued development of 3D printers to suit a broader variety of polymers for widespread applications of pharmaceutical additive manufacturing.

Hot-Melt Extrusion: a Roadmap for Product Development

Hot-melt extrusion has found extensive application as a feasible pharmaceutical technological option over recent years. HME applications include solubility enhancement, taste masking, and sustained drug release. As bioavailability enhancement is a hot topic of today's science, one of the main applications of HME is centered on amorphous solid dispersions. This review describes the most significant aspects of HME technology and its use to prepare solid dispersions as a drug formulation strategy to enhance the solubility of poorly soluble drugs. It also addresses molecular and thermodynamic features critical for the physicochemical properties of these systems, mainly in what concerns miscibility and physical stability. Moreover, the importance of applying the Quality by Design philosophy in drug development is also discussed, as well as process analytical technologies in pharmaceutical HME monitoring, under the current standards of product development and regulatory guidance. Graphical Abstract.

Coupling hot melt extrusion and fused deposition modeling: Critical properties for successful performance

Interest in 3D printing for pharmaceutical applications has increased in recent years. Compared to other 3D printing techniques, hot melt extrusion (HME)-based fused deposition modeling (FDM) 3D printing has been the most extensively investigated for patient-focused dosage. HME technology can be coupled with FDM 3D printing as a continuous manufacturing process. However, the crucial pharmaceutical polymers, formulation and process parameters must be investigated to establish HME-coupled FDM 3D printing. These advancements will lead the way towards developing continuous drug delivery systems for personalized therapy. This brief overview classifies pharmaceutical additive manufacturing, Hot Melt Extrusion, and Fused Deposition Modeling 3D printing techniques with a focus on coupling HME and FDM 3D printing processes. It also provides insights on the critical material properties, process and equipment parameters and limitations of successful HME-coupled FDM systems.

Hot Melt Extrusion and its Application in 3D Printing of Pharmaceuticals

Hot Melt Extrusion (HME) is a continuous pharmaceutical manufacturing process that has been extensively investigated for solubility improvement and taste masking of active pharmaceutical ingredients. Recently, it is being explored for its application in 3D printing. 3D printing of pharmaceuticals allows flexibility of dosage form design, customization of dosage form for personalized therapy and the possibility of complex designs with the inclusion of multiple actives in a single unit dosage form. Fused Deposition Modeling (FDM) is a 3D printing technique with a variety of applications in pharmaceutical dosage form development. FDM process requires a polymer filament as the starting material that can be obtained by hot melt extrusion. Recent reports suggest enormous applications of a combination of hot melt extrusion and FDM technology in 3D printing of pharmaceuticals and need to be investigated further. This review in detail describes the HME process, along with its application in 3D printing. The review also summarizes the published reports on the application of HME coupled with 3D printing technology in drug delivery.

The preparation of lipid-based drug delivery system using melt extrusion

Melt extrusion of lipids is versatile with high applicability in the pharmaceutical industry. The formulations prepared can be easily customized depending on the requirements, and have the potential to open a window on personalized medicine.

Development and Optimisation of Novel Polymeric Compositions for Sustained Release Theophylline Caplets (PrintCap) via FDM 3D Printing

This study reports a thorough investigation combining hot-melt extrusion technology (HME) and a low-cost fused deposition modelling (FDM) 3D printer as a continuous fabrication process for a sustained release drug delivery system. The successful implementation of such an approach presented herein allows local hospitals to manufacture their own medical and pharmaceutical products on-site according to their patients’ needs. This will help save time from waiting for suitable products to be manufactured off-site or using traditional manufacturing processes. The filaments were produced by optimising various compositions of pharmaceutical-grade polymers, such as hydroxypropyl cellulose (HPC), Eudragit^® (RL PO), and polyethylene glycol (PEG), whereas theophylline was used as a model thermally stable drug. For the purpose of the study, twin-screw hot-melt extrusion (HME) was implemented from the view that it would result in the formation of solid dispersion of drug in the polymeric carrier matrices by means of high shear mixing inside the heated barrel. Four filament compositions consisting of different ratios of polymers were produced and their properties were assessed. The mechanical characterisation of the filaments revealed quite robust properties of the filaments suitable for FDM 3D printing of caplets (PrintCap), whereas the solid-state analyses conducted via DSC and XRD showed amorphous nature of the crystalline drug dispersed in the polymeric matrices. Moreover, the surface analysis conducted via SEM showed a smooth surface of the produced filaments as well as caplets where no drug crystals were visible. The in vitro drug release study showed a sustained release profile over 10 h where about 80% of the drug was released from the printed dosage forms. This indicates that our optimised 3D printed caplets could be suitable for the development of sustained release on-demand drug delivery systems.

Recent Advances in Understanding the Micro- and Nanoscale Phenomena of Amorphous Solid Dispersions

Many pharmaceutical drugs in the marketplace and discovery pipeline suffer from poor aqueous solubility, thereby limiting their effectiveness for oral delivery. The use of an amorphous solid dispersion (ASD), a mixture of an active pharmaceutical ingredient and a polymer excipient, greatly enhances the aqueous dissolution performance of a drug without the need for chemical modification. Although this method is versatile and scalable, deficient understanding of the interactions between drugs and polymers inhibits ASD rational design. This current Review details recent progress in understanding the mechanisms that control ASD performance. In the solid-state, the use of high-resolution theoretical, computational, and experimental tools resolved the influence of drug/polymer phase behavior and dynamics on stability during storage. During dissolution in aqueous media, novel characterization methods revealed that ASDs can form complex nanostructures, which maintain and improve supersaturation of the drug. The studies discussed here illustrate that nanoscale phenomena, which have been directly observed and quantified, strongly affect the stability and bioavailability of ASD systems, and provide a promising direction for optimizing drug/polymer formulations.

Inline UV/Vis spectroscopy as PAT tool for hot-melt extrusion

Hot-melt extrusion on co-rotating twin screw extruders is a focused technology for the production of pharmaceuticals in the context of Quality by Design. Since it is a continuous process, the potential for minimizing product quality fluctuation is enhanced. A typical application of hot-melt extrusion is the production of solid dispersions, where an active pharmaceutical ingredient (API) is distributed within a polymer matrix carrier. For this dosage form, the product quality is related amongst others to the drug content. This can be monitored on- or inline as critical quality attribute by a process analytical technology (PAT) in order to meet the specific requirements of Quality by Design. In this study, an inline UV/Vis spectrometer from ColVisTec was implemented in an early development twin screw extruder and the performance tested in accordance to the ICH Q2 guideline. Therefore, two API (carbamazepine and theophylline) and one polymer matrix (copovidone) were considered with the main focus on the quantification of the drug load. The obtained results revealed the suitability of the implemented PAT tool to quantify the drug load in a typical range for pharmaceutical applications. The effort for data evaluation was minimal due to univariate data analysis, and in combination with a measurement frequency of 1 Hz, the system is sufficient for real-time data acquisition.

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

INTRODUCTION

Currently, hot melt extrusion (HME) is a promising technology in the pharmaceutical industry, as evidenced by its application to manufacture various FDA-approved commercial products in the market. HME is extensively researched for enhancing the solubility and bioavailability of poor water-soluble drugs, taste masking, and modifying release in drug delivery systems. Additionally, its other novel opportunities or pharmaceutical applications, and capability for continuous manufacturing are being investigated. This efficient, industrially scalable, solvent-free, continuous process can be easily automated and coupled with other novel platforms for continuous manufacturing of pharmaceutical products.

AREAS COVERED

This review focuses on updates on solubility enhancement of poorly water-soluble drugs and process analytical tools such as UV/visible spectrophotometry; near-infrared spectroscopy; Raman spectroscopy; and rheometry for continuous manufacturing, with a special emphasis on fused deposition modeling 3D printing.

EXPERT OPINION

The strengths, weakness, opportunities, threats (SWOT) and availability of commercial products confirmed wide HME applicability in pharmaceutical research. Increased interest in continuous manufacturing processes makes HME a promising strategy for this application. However, there is a need for extensive research using process analytical tools to establish HME as a dependable continuous manufacturing process.

Continuous Manufacturing in Pharmaceutical Process Development and Manufacturing

The pharmaceutical industry has found new applications for the use of continuous processing for the manufacture of new therapies currently in development. The transformation has been encouraged by regulatory bodies as well as driven by cost reduction, decreased development cycles, access to new chemistries not practical in batch, improved safety, flexible manufacturing platforms, and improved product quality assurance. The transformation from batch to continuous manufacturing processing is the focus of this review. The review is limited to small, chemically synthesized organic molecules and encompasses the manufacture of both active pharmaceutical ingredients (APIs) and the subsequent drug product. Continuous drug product is currently used in approved processes. A few examples of production of APIs under current good manufacturing practice conditions using continuous processing steps have been published in the past five years, but they are lagging behind continuous drug product with respect to regulatory filings.

Characterization of the Solid Physical State of API and Its Distribution in Pharmaceutical Hot Melt Extrudates Using Terahertz Raman Imaging

In this study, a method employing THz Raman imaging to characterize the solid state of acetaminophen within a solid dispersion prepared by hot melt extrusion was reported. The peak at 89 cm^-1 originating from the crystalline lattice vibrations provides unambiguous discrimination between crystalline and amorphous N-acetyl-para-aminophenol (APAP; acetaminophen) contents in the hot melt extrusion (HME) extrudates. Extrudates from four different HME processes (two different temperatures and two levels of screw speeds) were analyzed and compared. The results show that both high process temperature and high screw speed favor the formation of amorphous APAP solid dispersions. Finally, the high spatial resolution (~ 1 μm) Raman images of the extrudates prepared at 170°C and 200 rpm show a near-complete amorphous APAP dispersion in an HPMC matrix, confirming an efficient HME process. The study demonstrates that THz Raman imaging is ideally suited for the identification of different solid physical states of the APIs in a polymer matrix, and provides direct visualization of their distribution in HME extrudates.

Raman Spectroscopy for Process Analytical Technologies of Pharmaceutical Secondary Manufacturing

As the process analytical technology (PAT) mindset is progressively introduced and adopted by the pharmaceutical companies, there is an increasing demand for effective and versatile real-time analyzers to address the quality assurance challenges of drug manufacturing. In the last decades, Raman spectroscopy has emerged as one of the most promising tools for non-destructive and fast characterization of the pharmaceutical processes. This review summarizes the achieved results of the real-time application of Raman spectroscopy in the field of the secondary manufacturing of pharmaceutical solid dosage forms, covering the most common secondary process steps of a tablet production line. In addition, the feasibility of Raman spectroscopy for real-time control is critically reviewed, and challenges and possible approaches to moving from real-time monitoring to process analytically controlled technologies (PACT) are discussed.

Application of Online Near Infrared for Process Understanding of Spray-Drying Solution Preparation

Solution preparation is the first unit operation of the manufacturing process for spray-dried solid dispersions. Visual inspection and offline high-performance liquid chromatography analysis are routinely used to assess the solution preparation end point as well as the final solution composition. However, the accuracy and appropriateness of these approaches are challenged by the scale of production and solvent evaporation during sample handling. Thus an appropriate online process analytical tool is needed to improve process and quality control for the solution preparation process. The objective of this report is to develop near infrared (NIR) models for real-time monitoring of the spray solution preparation process. These models were built and refined via 2 different experiments designs with different production scale. The potency of spray-dried intermediate was analyzed by high-performance liquid chromatography and used to verify the quantitative model. The results indicated that the quantitative NIR models can be used to predict the active pharmaceutical ingredient concentration of the final spray solution accurately with a standard error of prediction of 2.4 wt%. Based on this investigation, online NIR was deemed to be a suitable analytical tool on process and quality control for spray solution preparation.

The application of temperature-composition phase diagrams for hot melt extrusion processing of amorphous solid dispersions to prevent residual crystallinity

Hot melt extrusion (HME) can be used to produce amorphous solid dispersions (ASDs) at temperatures below the drug's melting point if the drug and polymer exhibit melting point depression. However, the risk of residual crystallinity becomes significant. The purpose of this study was to apply the temperature-composition phase diagram to the HME process, correlating process conditions to ASD residual crystallinity, and identifying the formulation critical temperature, which defines the theoretical minimum processing temperature. The phase diagram of indomethacin (IDM) and polyvinylpyrrolidone/vinyl acetate copolymer (PVPVA) was generated using melting point depression measurements coupled with Flory-Huggins theory. Extrudates were manufactured above, at, and below the formulation critical temperature (T_c) as identified from the phase diagram, with a range of residence times, and characterized for crystallinity. Below the T_c, a fully amorphous sample could not be prepared. Above T_c, sufficient residence time led to amorphous samples. A processing operating design space diagram with three regimes was generated to correlate temperature and residence time factors with process outcome. In conclusion, phase diagrams provide a rational basis for designing hot melt extrusion processes of amorphous solid dispersions to minimize residual crystalline content, delineating the minimum processing temperature based on thermodynamic considerations.

Co-Amorphous Solid Dispersions for Solubility and Absorption Improvement of Drugs: Composition, Preparation, Characterization and Formulations for Oral Delivery

The amorphous solid state offers an improved apparent solubility and dissolution rate. However, due to thermodynamic instability and recrystallization tendencies during processing, storage and dissolution, their potential application is limited. For this reason, the production of amorphous drugs with adequate stability remains a major challenge and formulation strategies based on solid molecular dispersions are being exploited. Co-amorphous systems are a new formulation approach where the amorphous drug is stabilized through strong intermolecular interactions by a low molecular co-former. This review covers several topics applicable to co-amorphous drug delivery systems. In particular, it describes recent advances in the co-amorphous composition, preparation and solid-state characterization, as well as improvements of dissolution performance and absorption are detailed. Examples of drug-drug, drug-carboxylic acid and drug-amino acid co-amorphous dispersions interacting via hydrogen bonding, π−π interactions and ionic forces, are presented together with corresponding final dosage forms.

Hot Melt Extrusion: Highlighting Physicochemical Factors to Be Investigated While Designing and Optimizing a Hot Melt Extrusion Process

Hot-melt extrusion (HME) is a well-accepted and extensively studied method for preparing numerous types of drug delivery systems and dosage forms. It offers several advantages: no solvents are required, it is easy to scale up and employ on the industrial level, and, in particular, it offers the possibility of improving drug bioavailability. HME involves the mixing of a drug with one or more excipients, in general polymers and even plasticizers, which can melt, often forming a solid dispersion of the drug in the polymer. The molten mass is extruded and cooled, giving rise to a solid material with designed properties. This process, which can be realized using different kinds of special equipment, may involve modifications in the drug physicochemical properties, such as chemical, thermal and mechanical characteristics thus affecting the drug physicochemical stability and bioavailability. During process optimization, the evaluation of the drug solid state and stability is thus of paramount importance to guarantee stable drug properties for the duration of the drug product shelf life. This manuscript reviews the most important physicochemical factors that should be investigated while designing and optimizing a hot melt extrusion process, and by extension, during the different pre-formulation, formulation and process, and post-formulation phases. It offers a comprehensive evaluation of the chemical and thermal stability of extrudates, the solid physical state of extrudates, possible drug-polymer interactions, the miscibility/solubility of the drug-polymer system, the rheological properties of extrudates, the physicomechanical properties of films produced by hot melt extrusion, and drug particle dissolution from extrudates. It draws upon the last ten years of research, extending inquiry as broadly as possible.

Melt extrusion with poorly soluble drugs - An integrated review

Over the last few decades, hot melt extrusion (HME) has emerged as a successful technology for a broad spectrum of applications in the pharmaceutical industry. As indicated by multiple publications and patents, HME is mainly used for the enhancement of solubility and bioavailability of poorly soluble drugs. This review is focused on the recent reports on the solubility enhancement via HME and provides an update for the manufacturing/scaling up aspects of melt extrusion. In addition, drug characterization methods and dissolution studies are discussed. The application of process analytical technology (PAT) tools and use of HME as a continuous manufacturing process may shorten the drug development process; as a result, the latter is becoming the most widely utilized technique in the pharmaceutical industry. The advantages, disadvantages, and practical applications of various PAT tools such as near and mid-infrared, ultraviolet/visible, fluorescence, and Raman spectroscopies are summarized, and the characteristics of other techniques are briefly discussed. Overall, this review also provides an outline for the currently marketed products and analyzes the strengths, weaknesses, opportunities and threats of HME application in the pharmaceutical industry.