Continuous Formulation Approaches of Amorphous Solid Dispersions: Significance of Powder Flow Properties and Feeding Performance

A novel Posaconazole oral formulation using spray dried solid dispersion technology: in-vitro and in-vivo study

SD (solid dispersion) technology is one of the well-recognized solubility enhancement methods; but the use of versatile carriers in ASD (amorphous SD) to achieve the added advantage of modified release along with solubility improvement is an emerging area of exploration. Spray drying is a widely used technology with excellent scalability and product attributes. The SD carriers explored were Soluplus®, possessing excellent solubilization properties that may enhance bioavailability and is suitable for innovative processing, and Gelucire 43/01, a lipid polymer utilized in a non-effervescent-based floating gastro-retentive DDS for the modified release of API. The CPPs of spray drying were screened during preliminary trials, and the formulation variables were optimized using a 32 Full Factorial Design. All nine batches were evaluated for % yield, % drug content, flow properties, floating behavior, saturation solubility, and in-vitro drug release in 0.1 N HCl. The optimized batch characterized based on DSC (differential scanning calorimetry) and PXRD (powder X-ray diffraction) confirmed the amorphous nature of entrapped drug in SDD (spray-dried dispersion). Particle size analysis and SEM (scanning electron microscopy) demonstrated micron size irregular shaped particles. Residual solvent analysis by GCMS-HS confirmed the elimination of organic solvents from SDD. The optimized batch was found stable after 6 months stability study as per ICH guidelines. In-vivo roentgenography study in New Zealand white rabbit showed the residence of SDD in gastric environment for sufficient time. The pharmacokinetic study was performed in male Sprague-Dawley rats to determine the bioavailability of developed SDD based product in fasting and fed conditions, and to compare the data with marketed Noxafil formulation. The current research is focused on the development of a novel ternary SDD (spray-dried dispersion)-based gastro-retentive formulation for an anti-fungal drug Posaconazole.

HPMCAS-Based Amorphous Solid Dispersions in Clinic: A Review on Manufacturing Techniques (Hot Melt Extrusion and Spray Drying), Marketed Products and Patents

Today, therapeutic candidates with low solubility have become increasingly common in pharmaceutical research pipelines. Several techniques such as hot melt extrusion, spray drying, supercritical fluid technology, electrospinning, KinetiSol, etc., have been devised to improve either or both the solubility and dissolution to enhance the bioavailability of these active substances belonging to BCS Class II and IV. The principle involved in all these preparation techniques is similar, where the crystal lattice of the drug is disrupted by either the application of heat or dissolving it in a solvent and the movement of the fine drug particles is arrested with the help of a polymer by either cooling or drying to remove the solvent. The dispersed drug particles in the polymer matrix have higher entropy and enthalpy and, thereby, higher free energy in comparison to the crystalline drug. Povidone, polymethaacrylate derivatives, hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl methylcellulose acetate succinate derivatives are commonly used as polymers in the preparation of ASDs. Specifically, hydroxypropylmethylcellulose acetate succinate (HPMCAS)-based ASDs have become well established in commercially available products and are widely explored to improve the solubility of poorly soluble drugs. This article provides an analysis of two widely used manufacturing techniques for HPMCAS ASDs, namely, hot melt extrusion and spray drying. Additionally, details of HPMCAS-based ASD marketed products and patents have been discussed to emphasize the commercial aspect.

Development of Delayed Release Oral Formulation Comprising Esomeprazole Spray Dried Dispersion Utilizing Design of Experiment As An Optimization Strategy

Solid dispersion (SD) technology is one of the most widely preferred solubility enhancement methods, especially for Biopharmaceutics classification system class II and IV drugs. Since the last decade, its application for the dual purpose of solubility hike and modified release using novel carriers has been in demand for its added advantages. Spray drying is a commercially accepted technique with high aspects of scalability and product characteristics. The current study used spray-dried dispersion to design delayed release capsule for the proton pump inhibitor esomeprazole. The SD carrier hydroxypropyl methylcellulose acetate succinate-medium grade (HPMCAS-MF) enhanced solubility, inhibited precipitation of saturated drug solutions, and allowed enteric release owing to its solubility above pH 6. The proposed approach avoided compression, coating with enteric polymers, and the development of multi-particulate pellet-based formulations, improving manufacturing feasibility. The formulation was optimized using Box-Behnken design, considering significant formulation variables like HPMCAS-MF proportion and critical process parameters like feed flow rate and inlet temperature. The optimized spray-dried dispersion were characterized based on Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM) and also evaluated for solubility, in vitro drug release, residual solvent content, and stability testing. Response surface methodology optimization anticipated that formulation variables affected solubility and release profile, whereas CPPs affected yield. The design space was developed via overlay plot based on constraints specified to attain the desired response and validated using three checkpoint batches with desirability 1. FTIR showed active pharmaceutical ingredient-polymer compatibility. Particle size and SEM studies showed spherical particles with an average Z-value of 1.8 µ. DSC and PXRD confirmed SD's amorphous nature. The drug release investigation and release kinetics prediction utilizing DD-solver software showed a 2-h lag time with > 90% cumulative drug release up to 4 h for the DR formulation. ESM SDD were prepared by spray drying technique using the novel solid dispersion carrier HPMCAS-MF to serve the dual purpose of solubility enhancement and delayed release. The ratio of API:carrier and process variables like feed flow rate and inlet temperature were varied using the Box-Behnken Design to determine the design space of optimized product to procure the desired characteristics of solubility improvement compared to crystalline API and delayed release of PPI to avoid the degradation in the gastric environment. The developed formulation represents several benefits over the already existing marketed products.

Comprehensive powder flow characterization with reduced testing

Powder flow is a critical attribute of pharmaceutical blends to ensure tablet weight uniformity and production of tablets with consistent and reproducible properties. This study aims at characterizing different powder blends with a number of different rheologic techniques, in order to understand how particles' attributes and interaction between components within the formulation generate different responses when analysed by different rheological tests. Furthermore, this study intends on reducing the number of tests in early development phases, by selecting the ones that provide the best information about the flowability attributes of the pharmaceutical blends. This work considered two cohesive powders - spray-dried hydroxypropyl cellulose (SD HPMC) and micronized indomethacin (IND) - formulated with other four commonly used excipients [(lactose monohydrated (LAC), microcrystalline cellulose (MCC), magnesium stearate (MgSt) and colloidal silica (CS)]. The experimental results showed that powder flowability may be affected by materials particles' size, bulk density, morphology, and interactions with lubricant. In detail, parameters, such as angle of repose (AoR), compressibility percentage (CPS), and flow function coefficient (ff_c) have shown to be highly affected by the particle size of the materials present in the blends. On the other hand, the Specific Energy (SE) and the effective angle of internal friction (φe) showed to be more related with particle morphology and materials interaction with the lubricant. Since both ff_c and φe parameters are generated from the yield locus test, data suggest that a number of different powder flow features may be understood only by applying this test, avoiding redundant powder flow characterization, as well as extensive time and material spent in early development formulation stages.

Stability-Enhanced Ternary Solid Dispersions of Glyburide: Effect of Preparation Method on Physicochemical Properties

Introduction

Limited aqueous solubility and subsequent poor absorption and low bioavailability are the main challenges in oral drug delivery. Solid dispersion is a widely used formulation strategy to overcome this problem. Despite their efficiency, drug crystallization tendency and poor physical stability limited their commercial use. To overcome this defect, ternary solid dispersions of glyburide: sodium lauryl sulfate (SLS) and polyethylene glycol 4000 (PEG), were developed using the fusion (F) and solvent evaporation (SE) techniques and subsequently evaluated and compared.

Materials and Methods

Physicochemical and dissolution properties of the prepared ternary solid dispersions were evaluated using differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and dissolution test. Flow properties were also assessed using Carr's index and Hausner's ratio. The physical stability of the formulations was evaluated initially and after 12 months by comparing dissolution properties.

Results

Formulations prepared by both methods similarly showed significant improvements in dissolution efficiency and mean dissolution time compared to the pure drug. However, formulations that were prepared by SE showed a greater dissolution rate during the initial phase of dissolution. Also, after a 12-month follow-up, no significant change was observed in the mentioned parameters. The results of the infrared spectroscopy indicated that there was no chemical interaction between the drug and the polymer. The absence of endotherms related to the pure drug from thermograms of the prepared formulations could be indicative of reduced crystallinity or the gradual dissolving of the drug in the molten polymer. Moreover, formulations prepared by the SE technique revealed superior flowability and compressibility in comparison with the pure drug and physical mixture (ANOVA, P  <  0.05).

Conclusion

Efficient ternary solid dispersions of glyburide were successfully prepared by F and SE methods. Solid dispersions prepared by SE, in addition to increasing the dissolution properties and the possibility of improving the bioavailability of the drug, showed acceptable long-term physical stability with remarkably improved flowability and compressibility features.

Microfluidic Particle Engineering of Hydrophobic Drug with Eudragit E100─Bridging the Amorphous and Crystalline Gap

Co-processing active pharmaceutical ingredients (APIs) with excipients is a promising particle engineering technique to improve the API physical properties, which can lead to more robust downstream drug product manufacturing and improved drug product attributes. Excipients provide control over critical API attributes like particle size and solid-state outcomes. Eudragit E100 is a widely used polymeric excipient to modulate drug release. Being cationic, it is primarily employed as a precipitation inhibitor to stabilize amorphous solid dispersions. In this work, we demonstrate how co-processing of E100 with naproxen (NPX) (a model hydrophobic API) into monodisperse emulsions via droplet microfluidics followed by solidification via solvent evaporation allows the facile fabrication of compact, monodisperse, and spherical particles with an expanded range of solid-state outcomes spanning from amorphous to crystalline forms. Low E100 concentrations (≤26% w/w) yield crystalline microparticles with a stable NPX polymorph distributed uniformly across the matrix at a high drug loading (∼89% w/w). Structurally, E100 incorporation reduces the size of primary particles comprising the co-processed microparticles in comparison to neat API microparticles made using the same technique and the as-received API powder. This reduction in primary particle size translates into an increased internal porosity of the co-processed microparticles, with specific surface area and pore volume ∼9 times higher than the neat API microparticles. These E100-enabled structural modifications result in faster drug release in acidic media compared to neat API microparticles. Additionally, E100-NPX microparticles have a significantly improved flowability compared to neat API microparticles and as-received API powder. Overall, this study demonstrates a facile microfluidics-based co-processing method that broadly expands the range of solid-state outcomes obtainable with E100 as an excipient, with multiscale control over the key attributes and performance of hydrophobic API-laden microparticles.

Continuous Manufacturing and Molecular Modeling of Pharmaceutical Amorphous Solid Dispersions

Amorphous solid dispersions enhance solubility and oral bioavailability of poorly water-soluble drugs. The escalating number of drugs with poor aqueous solubility, poor dissolution, and poor oral bioavailability is an unresolved problem that requires adequate interventions. This review article highlights recent solubility and bioavailability enhancement advances using amorphous solid dispersions (ASDs). The review also highlights the mechanism of enhanced dissolution and the challenges faced by ASD-based products, such as stability and scale-up. The role of process analytical technology (PAT) supporting continuous manufacturing is highlighted. Accurately predicting interactions between the drug and polymeric carrier requires long experimental screening methods, and this is a space where computational tools hold significant potential. Recent advancements in data science, computational tools, and easy access to high-end computation power are set to accelerate ASD-based research. Hence, particular emphasis has been given to molecular modeling techniques that can address some of the unsolved questions related to ASDs. With the advancement in PAT tools and artificial intelligence, there is an increasing interest in the continuous manufacturing of pharmaceuticals. ASDs are a suitable option for continuous manufacturing, as production of a drug product from an ASD by direct compression is a reality, where the addition of multiple excipients is easy to avoid. Significant attention is necessary for ongoing clinical studies based on ASDs, which is paving the way for the approval of many new ASDs and their introduction into the market.

Downstream Processing of Amorphous and Co-Amorphous Olanzapine Powder Blends

The work evaluates the stability of amorphous and co-amorphous olanzapine (OLZ) in tablets manufactured by direct compression. The flowability and the compressibility of amorphous and co-amorphous OLZ with saccharin (SAC) and the properties of the tablets obtained were measured and compared to those of tablets made with crystalline OLZ. The flowability of the amorphous and mostly of the co-amorphous OLZ powders decreased in comparison with the crystalline OLZ due to the higher cohesiveness of the former materials. The stability of the amorphous and co-amorphous OLZ prior to and after tableting was monitored by XRPD, FTIR, and NIR spectroscopies. Tablets presented long-lasting amorphous OLZ with enhanced water solubility, but the release rate of the drug decreased in comparison with tablets containing crystalline OLZ. In physical mixtures made of crystalline OLZ and SAC, an extent of amorphization of approximately 20% was accomplished through the application of compaction pressures and dwell times of 155 MPa and 5 min, respectively. The work highlighted the stability of amorphous and co-amorphous OLZ during tableting and the positive effect of compaction pressure on the formation of co-amorphous OLZ, providing an expedited amorphization technique, given that the process development-associated hurdles were overcome.

Powder filling of electrospun material in vials: A proof-of-concept study

The present paper reports the powder filling of milled electrospun materials in vials, which contained voriconazole and sulfobutylether-β-cyclodextrin. High-speed electrospinning was used for the production of the fibrous sample, which was divided into 6 parts. Each portion was milled using different milling methods and sizes of sieves to investigate whether the milling influences the powder and filling properties. Bulk and tapped density tests, laser diffraction and angle of repose measurements were applied to characterize the milled powders, while a vibratory feeder was used for the feeding experiments. The correlation between the material property descriptors and the feeding responses was investigated by multivariate data analysis. Based on the results, three samples were chosen for the vial filling, which was accomplished with 3400 mg electrospun material containing 200 mg voriconazole, representative of the commercial product. The feed rate was set to fit the 240 g/h production rate of the electrospinning and the relative standard deviation of three repeated vial filling was determined to see the accuracy of the process. This research shows that by applying a suitable milling method it is possible to process electrospun fibers to a powder, which can be filled into vials and used as reconstitution dosage forms.

Continuous downstream processing of milled electrospun fibers to tablets monitored by near-infrared and Raman spectroscopy

Electrospinning is a technology for manufacture of nano- and micro-sized fibers, which can enhance the dissolution properties of poorly water-soluble drugs. Tableting of electrospun fibers have been demonstrated in several studies, however, continuous manufacturing of tablets have not been realized yet. This research presents the first integrated continuous processing of milled drug-loaded electrospun materials to tablet form supplemented by process analytical tools for monitoring the active pharmaceutical ingredient (API) content. Electrospun fibers of an amorphous solid dispersion (ASD) of itraconazole and poly(vinylpyrrolidone-co-vinyl acetate) were produced using high speed electrospinning and afterwards milled. The milled fibers with an average fiber diameter of 1.6 ± 0.9 µm were continuously fed with a vibratory feeder into a twin-screw blender, which was integrated with a tableting machine to prepare tablets with ~ 10 kN compression force. The blend of fibers and excipients leaving the continuous blender was characterized with a bulk density of 0.43 g/cm³ and proved to be suitable for direct tablet compression. The ASD content, and thus the API content was determined in-line before tableting and at-line after tableting using near-infrared and Raman spectroscopy. The prepared tablets fulfilled the USP <905> content uniformity requirement based on the API content of ten randomly selected tablets. This work highlights that combining the advantages of electrospinning (e.g. less solvent, fast and gentle drying, low energy consumption, and amorphous products with high specific surface area) and the continuous technologies opens a new and effective way in the field of manufacturing of the poorly water-soluble APIs.

Vacuum drum drying - A novel solvent-evaporation based technology to manufacture amorphous solid dispersions in comparison to spray drying and hot melt extrusion

In this study, a novel solvent-evaporation based technology to manufacture amorphous solid dispersions (ASDs) called vacuum drum drying (VDD) was assessed in comparison to the conventional technologies hot-melt extrusion (HME) and spray drying (SD). Ritonavir (15%w/w) embedded in copovidone/sorbitan monolaurate was used to investigate the impact on the ASD quality, material properties and in-vitro dissolution. All ASDs met the critical quality criteria: absence of drug substance related crystallinity, residual solvents below ICH limit (SD, VDD) and degradation products within specification limits. Clear differences in material properties such as particle morphology and size distribution, powder densities and flowability properties were observed. Overall, the milled extrudate showed superior material properties in terms of downstream processability. The VDD intermediate performed slightly better in terms of flowability and electrostatic behavior compared to the spray dried while showing comparably unfavorable densities. However, the dissolution data suggested no significant difference between the ASDs prepared by HME, SD, and VDD and thus, no change in bioavailability is expected. In conclusion, the VDD technology might be a viable alternative to manufacture ASDs - especially for thermosensitive and shear-sensitive compounds with potential to process formulations with high solid loads and viscosities while exhibiting higher throughputs at a lower footprint.

Bioavailability Improvement of Carbamazepine via Oral Administration of Modified-Release Amorphous Solid Dispersions in Rats

The purpose of this study was to improve the bioavailability of carbamazepine (CBZ), a poorly water-soluble antiepileptic drug, via modified-release amorphous solid dispersions (mr-ASD) by a thin film freezing (TFF) process. Three types of CBZ-mr-ASD with immediate-, delayed-, and controlled-release properties were successfully prepared with HPMC E3 (hydrophilic), L100-55 (enteric), and cellulose acetate (CA, lipophilic), defined as CBZ-ir-ASD, CBZ-dr-ASD, and CBZ-cr-ASD, respectively. A dry granulation method was used to prepare CBZ-mr-ASD capsule formulations. Various characterization techniques were applied to evaluate the physicochemical properties of CBZ-mr-ASD and the related capsules. The drug remained in an amorphous state when encapsulated within CBZ-mr-ASD, and the capsule formulation progress did not affect the performance of the dispersions. In dissolution tests, the preparations and the corresponding dosage forms similarly showed typical immediate-, delayed-, and controlled-release properties depending on the solubility of the polymers. Moreover, single-dose 24 h pharmacokinetic studies in rats indicated that CBZ-mr-ASD significantly enhanced the oral absorption of CBZ compared to that of crude CBZ. Increased oral absorption of CBZ was observed, especially in the CBZ-dr-ASD formulation, which showed a better pharmacokinetic profile than that of crude CBZ with 2.63- and 3.17-fold improved bioavailability of the drug and its main active metabolite carbamazepine 10,11-epoxide (CBZ-E).

Hot-Melt Extrusion as an Advantageous Technology to Obtain Effervescent Drug Products

Here, we assessed the feasibility of hot-melt extrusion (HME) to obtain effervescent drug products for the first time. For this, a combined mixture design was employed using paracetamol as a model drug. Extrudates were obtained under reduced torque (up to 0.3 Nm) at 100 °C to preserve the stability of the effervescent salts. Formulations showed vigorous and rapid effervescent disintegration (<3 min), adequate flow characteristics, and complete solubilization of paracetamol instantly after the effervescent reaction. Formulations containing PVPVA in the concentration range of 15–20% m/m were demonstrated to be sensitive to accelerated aging conditions, undergoing marked microstructural changes, since the capture of water led to the agglomeration and loss of their functional characteristics. HPMC matrices, in contrast, proved to be resistant to storage conditions in high relative humidity, showing superior performance to controls, including the commercial product. Moreover, the combined mixture design allowed us to identify significant interactions between the polymeric materials and the disintegrating agents, showing the formulation regions in which the responses are kept within the required levels. In conclusion, this study demonstrates that HME can bring important benefits to the elaboration of effervescent drug products, simplifying the production process and obtaining formulations with improved characteristics, such as faster disintegration, higher drug solubilization, and better stability.

Microwave-Induced In Situ Amorphization: A New Strategy for Tackling the Stability Issue of Amorphous Solid Dispersions

The thermodynamically unstable nature of amorphous drugs has led to a persistent stability issue of amorphous solid dispersions (ASDs). Lately, microwave-induced in situ amorphization has been proposed as a promising solution to this problem, where the originally loaded crystalline drug is in situ amorphized within the final dosage form using a household microwave oven prior to oral administration. In addition to circumventing issues with physical stability, it can also simplify the problematic downstream processing of ASDs. In this review paper, we address the significance of exploring and developing this novel technology with an emphasis on systemically reviewing the currently available literature in this pharmaceutical arena and highlighting the underlying mechanisms involved in inducing in situ amorphization. Specifically, in order to achieve a high drug amorphicity, formulations should be composed of drugs with high solubility in polymers, as well as polymers with high hygroscopicity and good post-plasticized flexibility of chains. Furthermore, high microwave energy input is considered to be a desirable factor. Lastly, this review discusses challenges in the development of this technology including chemical stability, selection criteria for excipients and the dissolution performance of the microwave-induced ASDs.

Enhanced Dissolution of Luteolin by Solid Dispersion Prepared by Different Methods: Physicochemical Characterization and Antioxidant Activity

Luteolin (LT) is a poorly soluble bioactive compound that suffered bioavailability problems after oral administration. Hence, the aim of the proposed research work was to formulate and investigate various solid dispersions (SDs) of LT in order to enhance its dissolution and bioactivity. LT-SD was prepared using polyethylene glycol 4000 (PEG 4000) as a carrier at the mass ratios of 1:1, 1:2, and 1:4. LT-SD was prepared using different methods including fusion (FU), solvent evaporation (SE), and microwave irradiation (MI) methods. The prepared LT-SD was duly characterized in terms of differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) and evaluated for dissolution and in vitro antioxidant activity. The results of DSC, XRD, SEM, IR, and NMR suggested the formation of LT-SD. After 90 min of the dissolution study, the results displayed that the % release of LT from prepared SD was significantly higher compared with the pure LT and its physical mixture dispersion (PMD). LT-SD prepared using the MI method displayed the maximum release of LT (i.e., 97.78 ± 4.41%) at a 1:2 mass ratio of LT:PEG 4000. The LT-SD prepared using the SE method displayed the maximum release of 93.78 ± 3.98% at a mass ratio of 1:4 of LT:PEG 4000. The SD prepared by the MI method showed enhanced dissolution due to higher aqueous solubility and the reduction of particle size. The solid-state characterization studies (DSC, XRD, SEM, IR, and NMR studies) suggested the morphological conversion of LT into the amorphous form from the crystalline state. The results of the antioxidant study revealed that the formation LT-SD displayed significantly higher radical scavenging activity than the pure LT. Therefore, SD obtained using PEG 4000 could be a potential strategy for maximizing the solubility, in vitro dissolution, and therapeutic efficacy of LT.