Solid-state characterization of Felodipine-Soluplus amorphous solid dispersions

A comprehensive overview of the role of intermolecular interactions in amorphous solid dispersions

Many recent studies have indicated that drug-polymer intermolecular interactions are an important aspect of amorphous solid dispersions (ASDs) and determine many of the properties of this type of formulations. In this review, a comprehensive overview is given of the latest insights with respect to intermolecular interactions in ASDs. The thermodynamic properties and theoretical considerations of the interactions are discussed, followed by a detailed and critical overview of the various solid-state analysis techniques used to probe interactions at the disposal of the formulation scientist. As the physical stability and the pharmaceutical performance of the ASD are its most crucial properties, the most recent understanding of the influence of drug-polymer interactions on these aspects is addressed as well. It is clear that intermolecular interactions may provide many advantages for ASDs but need to be weighed against the possible disadvantages. Further investigation into the interplay and trade-off between physical stability and dissolution properties is necessary in order to be able to take full advantage of the possible benefits of the interactions.

Quantification of soluplus for dissolution tests: SEC method development and validation

The quantification of both polymer and drug during the dissolution of an amorphous solid dispersion (ASD) in aqueous media arouses great interest and may aid in the formulation. However, the available quantification methods for polymer excipients are limited, expensive, and challenging compared to drugs. In this work, a size exclusion chromatography method (HPLC-SEC) was developed and validated to determine the concentration of a frequently used polymer excipient, Soluplus® (Sol). In order to develop a method for the quantification of dissolved Soluplus®, two methods (SEC-UV and SEC-RID) with two injection volumes were tested with standard solutions of three different batches of Soluplus. The developed HPLC-SEC-UV method showed acceptable linearity (R2 > 0.9990) for all batches of Soluplus, good accuracies above a concentration of 0.1 mg/mL (coefficient of variation < 2 %), relatively good precision at a concentration of 0.1 mg/mL (coefficient of variation < 2.5 %), and high recoveries at a concentration of 0.75 mg/mL (coefficient of variation < 0.5 %). The presence of Felodipine (Fel) and Lumefantrine (Lum) in the liquid media did not interfere with Soluplus quantification. The use of various surfactants, such as Tween® 80, Tween® 20, Span® 80, Span® 20, Kolliphor® TPGS, and sodium lauryl sulphate at a low concentration (0.005 mg/mL) did not show any effect on Soluplus® and did not interfere with Soluplus® quantification with any of the Soluplus batches. The addition of lithium bromide (LiBr) to the mobile phase within a concentration range of 0.05-1.0 M did not improve Soluplus® quantification.

Microscope-enabled disc dissolution system: Concordance between drug and polymer dissolution from an amorphous solid dispersion disc and visual disc degradation

A microscopic erosion time test was recently described to anticipate amorphous solid dispersion (ASD) drug load dispersibility limit, using 0.5 ml media volume. Studies here build upon this microscope-enabled method but focus on drug and polymer dissolution from an ASD disc, along with imaging. The objective was 1) to design and build a microscope-enabled disc dissolution system (MeDDiS) with a 900 mL dissolution volume and 2) assess the ability of MeDDiS imaging of dissolving discs to provide concordance with measured drug and polymer dissolution profiles. MeDDiS employed a digital microscope to image ASD discs and a one-liter vessel for dissolution. ASD discs containing ritonavir (5-50 % drug load) and PVPVA were fabricated and subjected to in vitro dissolution using MeDDiS, where disc diameter was quantified with time. Ritonavir and PVPVA release were also measured. Results indicate concordance between imaging and dissolution. Both found 25 % drug load to provide high drug and polymer release, but 30 % yielded low release. Quantitatively, MeDDiS images predicted drug and polymer release profiles, both above and below the drug load cliff. Overall, studies here describe a MeDDiS which has promised to anticipate drug and polymer dissolution, via imaging of dissolving discs, above and below the ASD drug load cliff.

Curcumin-loaded soluplus® based ternary solid dispersions with enhanced solubility, dissolution and antibacterial, antioxidant, anti-inflammatory activities

Amorphous solid dispersion (ASD) has emerged to be an outstanding strategy among multiple options available for improving solubility and consequently biological activity. Interestingly several binary SD systems continue to exhibit insufficient solubility over time. Therefore, the goal of current research was to design ternary amorphous solid dispersions (ASDs) of hydrophobic model drug curcumin (CUR) to enhance the solubility and dissolution rate in turn, presenting enhanced anti-bacterial, antioxidant and anti-inflammatory activity. For this purpose several ternary solid dispersions (TSDs) consisting of Soluplus®, Syloid® XDP 3150, Syloid® 244 and Poloxamer® 188 in combination with HPMC E5 (binary carrier) were prepared using solvent evaporation method. Both solubility and dissolution testing of prepared solid dispersion were performed to determine the increase in solubility and dissolution. Solid state investigation was carried out utilizing infrared spectroscopy, also known as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM),Differential scanning calorimetry (DSC) and X-ray diffraction (XRD).Optimized formulations were also tested for their biological effectiveness including anti-bacterial, anti-oxidant and anti-inflammatory activity. Amid all Ternary formulations F3 entailing 20 % soluplus® remarkably improved the solubility (186 μg/ml ± 3.95) and consequently dissolution (91 % ± 3.89 %) of curcumin by 3100 and 9 fold respectively. These finding were also supported by FTIR, SEM, XRD and DSC. In-vitro antibacterial investigation of F3 also demonstrated significant improvement in antibacterial activity against both gram positive (Staphylococcus aureus, Bacillus cereus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. Among all the tested strains Staphylococcus aureus was found to be most susceptible with a zone of inhibition of 24 mm ± 2.87. Antioxidant activity of F3 was also notably enhanced (93 % ± 5.30) in contrast to CUR (69 % ± 4.79). In vitro anti-inflammatory assessment also exhibited that F3 markedly protected BSA (bovine serum albumin) from denaturation with percent BSA inhibition of 80 % ± 3.16 in comparison to CUR (49 % ± 2.91). Hence, F3 could be an effective solid dispersion system for the delivery of model hydrophobic drug curcumin.

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.

Review of industrially recognized polymers and manufacturing processes for amorphous solid dispersion based formulations

Evolving therapeutic landscape through combinatorial chemistry and high throughput screening have resulted in an increased number of poorly soluble drugs. Drug delivery strategies quickly adapted to convert these drugs into successful therapies. Amorphous solid dispersion (ASD) technology is widely employed as a drug delivery strategy by pharmaceutical industries to overcome the challenges associated with these poorly soluble drugs. The development of ASD formulation requires an understanding of polymers and manufacturing techniques. A review of US FDA-approved ASD-based products revealed that only a limited number of polymers and manufacturing technologies are employed by pharmaceutical industries. This review provides a comprehensive guide for the selection and overview of polymers and manufacturing technologies adopted by pharmaceutical industries for ASD formulation. The various employed polymers with their underlying mechanisms for solution-state and solid-state stability are discussed. ASD manufacturing techniques, primarily implemented by pharmaceutical industries for commercialization, are presented in Quality by Design (QbD) format. An overview of novel excipients and progress in manufacturing technologies are also discussed. This review provides insights to the researchers on the industrially accepted polymers and manufacturing technology for ASD formulation that has translated these challenging drugs into successful therapies.

Amorphous Pterostilbene Delivery Systems Preparation-Innovative Approach to Preparation Optimization

The aim of our research was to improve the solubility and antioxidant activity of pterostilbene (PTR) by developing a novel amorphous solid dispersion (ASD) with Soluplus^® (SOL). DSC analysis and mathematical models were used to select the three appropriate PTR and SOL weight ratios. The amorphization process was carried out by a low-cost and green approach involving dry milling. An XRPD analysis confirmed the full amorphization of systems in 1:2 and 1:5 weight ratios. One glass transition (T_g) observed in DSC thermograms confirmed the complete miscibility of the systems. The mathematical models indicated strong heteronuclear interactions. SEM micrographs suggest dispersed PTR within the SOL matrix and a lack of PTR crystallinity, and showed that after the amorphization process, PTR-SOL systems had a smaller particle size and larger surface area compared with PTR and SOL. An FT-IR analysis confirmed that hydrogen bonds were responsible for stabilizing the amorphous dispersion. HPLC studies showed no decomposition of PTR after the milling process. PTR's apparent solubility and antioxidant activity after introduction into ASD increased compared to the pure compound. The amorphization process improved the apparent solubility by ~37-fold and ~28-fold for PTR-SOL, 1:2 and 1:5 w/w, respectively. The PTR-SOL 1:2 w/w system was preferred due to it having the best solubility and antioxidant activity (ABTS: IC₅₀ of 56.389 ± 0.151 µg·mL^-1 and CUPRAC: IC_0.5 of 82.52 ± 0.88 µg·mL^-1).

Recent Advances in Amorphous Solid Dispersions: Preformulation, Formulation Strategies, Technological Advancements and Characterization

Amorphous solid dispersions (ASDs) are among the most popular and widely studied solubility enhancement techniques. Since their inception in the early 1960s, the formulation development of ASDs has undergone tremendous progress. For instance, the method of preparing ASDs evolved from solvent-based approaches to solvent-free methods such as hot melt extrusion and Kinetisol^®. The formulation approaches have advanced from employing a single polymeric carrier to multiple carriers with plasticizers to improve the stability and performance of ASDs. Major excipient manufacturers recognized the potential of ASDs and began introducing specialty excipients ideal for formulating ASDs. In addition to traditional techniques such as differential scanning calorimeter (DSC) and X-ray crystallography, recent innovations such as nano-tomography, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray microscopy support a better understanding of the microstructure of ASDs. The purpose of this review is to highlight the recent advancements in the field of ASDs with respect to formulation approaches, methods of preparation, and advanced characterization techniques.

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.

Deep Learning-Based Prediction of Physical Stability considering Class Imbalance for Amorphous Solid Dispersions

This research is aimed at predicting the physical stability for amorphous solid dispersion by utilizing deep learning methods. We propose a prediction model that effectively learns from a small dataset that is imbalanced in terms of class. In order to overcome the imbalance problem, our model performs a hybrid sampling which combines synthetic minority oversampling technique (SMOTE) algorithm with edited nearest neighbor (ENN) algorithm and reduces the dimensionality of the dataset using principal component analysis (PCA) algorithm during data preprocessing. After the preprocessing, it performs the learning process using a carefully designed neural network of simple but effective structure. Experimental results show that the proposed model has faster training convergence speed and better test performance compared to the existing DNN model. Furthermore, it significantly reduces the computational complexity of both training and test processes.

Benzoic acid complexes with Eudragit E100®: New alternative antimicrobial preservatives

Given that the use of some preservatives in cosmetics has been restricted, novel alternative preservatives are needed. The aim of this study was to characterize the physicochemical and antimicrobial properties of two polyelectrolyte complexes (EuB₁₀₀ and EuB₇₅Cl₂₅), which were developed through hot melt extrusion (HME) using benzoic acid (BA) and Eudragit E100. Based on phase diagrams and an experimental statistical design, the solubility of the acid in the polymer and the HME conditions were established. Intermolecular interactions were evaluated through Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRPD). Release behavior was determined for the systems. Antibacterial activity and ζ-potential were determined on Escherichia coli. FTIR revealed acid-base interaction, and XPS showed that the percentages of protonated nitrogen N1s were 13.5% for EuB₁₀₀ and 20.3% for EuB₇₅Cl₂₅. The BA released showed a non-Fickian behavior, and a satisfactory antibacterial activity against E. coli was demonstrated at pH 6.9. The complexes modified ζ-potential, destabilizing the membrane functionality of E. coli. These complexes are potential antimicrobial preservatives with a greater spectrum of action, with bactericidal activity against E. coli in a wider pH range than uncomplexed BA, even at pH 6.9.

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.

Amorphous Solid Dispersions of Felodipine and Nifedipine with Soluplus®: Drug-Polymer Miscibility and Intermolecular Interactions

The objective of this study was to investigate thermodynamic and kinetic miscibility for two structurally similar model compounds nifedipine (NIF) and felodipine (FEL) when formulated as amorphous solid dispersions (ASDs) with an amphiphilic polymer Soluplus®. Thermodynamic miscibility was studied via melting point depression approach for the two systems. The Flory Huggins theory was used to calculate the interaction parameter and generate the phase diagrams. It was shown that NIF was more miscible in Soluplus® than FEL. The nature of drug polymer interactions was studied by fourier transform infra-red spectroscopy (FTIR) and solid-state nuclear magnetic resonance spectroscopy (ssNMR). The data from spectroscopic analyses showed that both the drugs interacted with Soluplus® through hydrogen bonding interactions. Furthermore, ¹³C ssNMR data was used to get quantitative estimate of the extent of hydrogen bonding for ASDs samples. Proton relaxation measurements were carried out on ASDs in order to evaluate phase heterogeneity on two different length scales of mixing. The data suggested that better phase homogeneity in NIF:SOL systems especially for lower Soluplus® content ASDs on smaller domains. This could be explained by understanding the extent of hydrogen bonding interactions for these two systems. This study highlights the need to consider thermodynamic and kinetic mixing, when formulating ASDs with the goal of understanding phase mixing between drug and polymer.

The preparation of felodipine/zein amorphous solid dispersions and in vitro evaluation using a dynamic gastrointestinal system

ABSTRCT Felodipine has been widely used as a poorly water-soluble model drug for various studies to improve its oral bioavailability and in vivo efficacy. In this study, we developed amorphous solid dispersions (ASDs) via spray drying to enhance the bioavailability of felodipine through using natural zein protein as a novel polymeric excipient. The solid state characterization results demonstrated a single glass transition temperature (T_g ) around 128.6 °C and good physical stability post 3 months accelerated study under the condition of 40 °C and 75% relative humidity (RH), which is possibly accounted for the molecular immobilization and hydrogen bonding interactions between felodipine and zein. By combining the in vitro dissolution study with TIM-1 gastrointestinal simulation investigation, it is indicated that felodipine was rapidly released from the ASD in 30 mins, and the supersaturation of felodipine was well maintained over 6 h, which resulted in a significant enhancement of felodipine bioavailability during simulated digestive processes in the upper GI tract. This study suggests that spray drying combined with natural excipient zein is an efficient formulation strategy for the development of ASDs with enhanced aqueous solubility and bioavailability.

Predicting physical stability of solid dispersions by machine learning techniques

Amorphous solid dispersion (SD) is an effective solubilization technique for water-insoluble drugs. However, physical stability issue of solid dispersions still heavily hindered the development of this technique. Traditional stability experiments need to be tested at least three to six months, which is time-consuming and unpredictable. In this research, a novel prediction model for physical stability of solid dispersion formulations was developed by machine learning techniques. 646 stability data points were collected and described by over 20 molecular descriptors. All data was classified into the training set (60%), validation set (20%), and testing set (20%) by the improved maximum dissimilarity algorithm (MD-FIS). Eight machine learning approaches were compared and random forest (RF) model achieved the best prediction accuracy (82.5%). Moreover, the RF models revealed the contribution of each input parameter, which provided us the theoretical guidance for solid dispersion formulations. Furthermore, the prediction model was confirmed by physical stability experiments of 17β-estradiol (ED)-PVP solid dispersions and the molecular mechanism was investigated by molecular modeling technique. In conclusion, an intelligent model was developed for the prediction of physical stability of solid dispersions, which benefit the rational formulation design of this technique. The integrated experimental, theoretical, modeling and data-driven AI methodology is also able to be used for future formulation development of other dosage forms.

Analytical and Computational Methods for the Estimation of Drug-Polymer Solubility and Miscibility in Solid Dispersions Development

The development of stable solid dispersion formulations that maintain desired improvement of drug dissolution rate during the entire shelf life requires the analysis of drug-polymer solubility and miscibility. Only if the drug concentration is below the solubility limit in the polymer, the physical stability of solid dispersions is guaranteed without risk for drug (re)crystallization. If the drug concentration is above the solubility, but below the miscibility limit, the system is stabilized through intimate drug-polymer mixing, with additional kinetic stabilization if stored sufficiently below the mixture glass transition temperature. Therefore, it is of particular importance to assess the drug-polymer solubility and miscibility, to select suitable formulation (a type of polymer and drug loading), manufacturing process, and storage conditions, with the aim to ensure physical stability during the product shelf life. Drug-polymer solubility and miscibility can be assessed using analytical methods, which can detect whether the system is single-phase or not. Thermodynamic modeling enables a mechanistic understanding of drug-polymer solubility and miscibility and identification of formulation compositions with the expected formation of the stable single-phase system. Advance molecular modeling and simulation techniques enable getting insight into interactions between the drug and polymer at the molecular level, which determine whether the single-phase system formation will occur or not.

Solubility and bioavailability enhancement study of lopinavir solid dispersion matrixed with a polymeric surfactant - Soluplus

As a biopharmaceutical classification system Class IV drug, lopinavir (LPV) shows relatively poor water solubility and permeation in vivo. In the study, we developed novel solid dispersions (SD) of LPV to improve its bioavailability and to describe their overall behaviors. By employing solvent evaporation for a preliminary formulation screening, the SDs of LPV-polymer-sorbitan monolaurate (SBM, as the wetting agent) at 1:4:0.4 (w/w) dramatically enhanced the LPV dissolution in a non-sink medium, and then hot-melt extrusion (HME) was applied to improve the dissolution further. A hydrophilic polymer - Kollidon VA 64 (VA64) and a polymeric surfactant Soluplus were employed as matrix respectively in the optimized formulations. The dissolution profiles of extrudates were significantly higher than those of SDs prepared with solvent-evaporation method. It was attributed to the stronger intermolecular interactions between LPV and the polymers in the HME process, which was also supported by the stability analysis after 6 months storage under 25 °C/60% RH. The differential scanning calorimetry, fourier transform infrared spectroscopy and equilibrium studies showed VA64 only created hydrogen bonding (H-bond) with LPV, but Soluplus generated both H-bond and micelle thanks to its amphiphilic structure. In addition, the bioavailability of LPV in Soluplus matrixed extrudate was 1.70-fold of VA64 matrixed extrudate and 3.70-fold of LPV crystal. In situ permeability and Caco-2 cell transport studies revealed that Soluplus significantly enhanced the permeability of LPV through rat intestine and Caco-2 cell monolayers by P-glycoprotein (P-gp) inhibition. Herein, Soluplus matrixed extrudate improved the LPV bioavailability through three mechanisms: H-bond with LPV, micelle formation in water and P-gp inhibition in vivo. These unique advantages of Soluplus suggested it is a promising carrier for poorly water soluble drugs, especially the substrates of P-gp.

Self-nanomicellizing solid dispersion of edaravone: part I - oral bioavailability improvement

Background

Edaravone (EDR) is known for its free radical scavenging, antiapoptotic, antinecrotic, and anticytokine effects in neurological and non-neurological diseases. It is currently available clinically as Radicava^® and Radicut^®, intravenous medications, recently approved for the treatment of amyotrophic lateral sclerosis and cerebral infarction. However, the oral use of EDR is still restricted by its poor oral bioavailability (BA) due to poor aqueous solubility, stability, rapid metabolism, and low permeability. The present study reports the development of novel EDR formulation (NEF) using self-nanomicellizing solid dispersion (SNMSD) strategy with the aim to enable its oral use.

Materials and methods

The selection of a suitable carrier for the development of NEF was performed based on the miscibility study. The optimization of EDR-to-carrier ratio was conducted via kinetic solubility study after preparing SNMSDs using solvent evaporation technique. The drug–polymer carrier interaction and self-nanomicellizing properties of NEF were investigated with advanced characterization studies. In vitro permeation, metabolism, and dissolution study was carried out to examine the effect of the presence of a carrier on physico-chemical properties of EDR. Additionally, the dose-dependent pharmacokinetic study of NEF was conducted and compared with the EDR suspension.

Results

Soluplus^® (SOL) as a carrier was selected based on the potential for improving aqueous solubility. The NEF containing EDR and SOL (1:5) resulted in the highest enhancement in aqueous solubility (17.53-fold) due to amorphization, hydrogen bonding interaction, and micellization. Moreover, the NEF demonstrated significant improvement in metabolism, permeability, and dissolution profile of EDR. Furthermore, the oral BA of NEF showed 10.2-, 16.1-, and 14.8-fold enhancement compared to EDR suspension at 46, 138, and 414 µmol/kg doses.

Conclusion

The results demonstrated that SNMSD strategy could serve as a promising way to enhance EDR oral BA and NEF could be a potential candidate for the treatment of diseases in which oxidative stress plays a key role in their pathogenesis.

Screen for Inhibitors of Crystal Growth to Identify Desirable Carriers for Amorphous Solid Dispersions Containing Felodipine

The solvent-shift method was used to identify appropriate polymers that inhibit the growth of felodipine crystals by monitoring particle size in supersaturated drug solutions in the presence of different polymers. We speculated that there would be an intermolecular interaction between the selected polymer (zein) and felodipine by extrapolating the inhibitory effect on crystal growth and then used the selected polymer as a carrier to prepare solid dispersions. The formulations were characterized by crystalline properties, thermodynamics of mixing, dissolution behavior, and physical stability. Powder x-ray diffraction and differential scanning calorimetry experiments indicated that amorphous solid dispersions were formed when the proportion of felodipine was < 30% (w/w). Stability tests showed that a solid dispersion with 20% felodipine remained in an amorphous state and was stable under accelerated storage conditions for 6 months. The dissolution rates of solid dispersions were significantly greater than those of the active pharmaceutical ingredient or physical mixtures. Analysis by Fourier-transform infrared spectroscopy and Raman microspectroscopy indicated the formation of intermolecular interactions between zein and felodipine. The study demonstrates the successful application of the chosen polymer as a carrier in solid dispersions and validates the concept of extrapolating the inhibitory effect on crystal growth to intermolecular interactions.

Polymer blends used to develop felodipine-loaded hollow microspheres for improved oral bioavailability

Felodipine (FD) has been widely used in anti-hypertensive treatment. However, it has extremely low aqueous solubility and poor bioavailability. To address these problems, FD hollow microspheres as multiple-unit dosage forms were synthesized by a solvent diffusion evaporation method. Particle size of the hollow microspheres, types of ethylcellulose (EC), amounts of EC, polyvinyl pyrrolidone (PVP) and FD were investigated based on an orthogonal experiment of three factors and three levels. In addition, the release kinetics in vitro and pharmacokinetics in beagle dogs of the optimized FD hollow microspheres was investigated and compared with Plendil (commercial FD sustained-release tablets) as a single-unit dosage form. Results showed that the optimal formulation was composed of EC_{10 cp}:PVP:FD (0.9:0.16:0.36, w/w). The FD hollow microspheres were globular with a hollow structure and have high drug loading (17.69±0.44%) and floating rate (93.82±4.05%) in simulated human gastric fluid after 24h. Pharmacokinetic data showed that FD hollow microspheres exhibited sustained-release behavior and significantly improved relative bioavailability of FD compared with the control. Pharmacodynamic study showed that the FD hollow microspheres could effectively lower blood pressure. Therefore, these findings demonstrated that the hollow microspheres were an effective sustained-release delivery system for FD.

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.

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.