Molecular Interactions in Solid Dispersions of Poorly Water-Soluble Drugs

Solid dispersion systems for enhanced dissolution of poorly water-soluble candesartan cilexetil: In vitro evaluation and simulated pharmacokinetics studies

BACKGROUND

Candesartan cilexetil (CC) is a selective angiotensin II receptor antagonist widely used to treat hypertension. CC is a substrate of P-glycoprotein (P-gp), causing its efflux to the intestinal lumen. It is also practically insoluble in water and has low oral bioavailability (14%). Thus, the current study aims to improve the in vitro dissolution of CC by developing solid dispersion systems (SDSs) and corroborating the in vitro results using a simulated pharmacokinetics study.

METHODS

The SDSs were prepared using polyvinyl pyrrolidone (PVP) as a water-soluble polymer, Eudragit E100 (EE100) as a pH-dependent soluble carrier, and a combination of these two polymers. The saturation solubility and the dissolution rate studies of the prepared systems in three dissolution media were performed. The optimized system SE-EE5 was selected for further investigations, including DSC, XRD, FTIR, FESEM, DLS, TSEM, IVIVC convolution study, and stability studies.

RESULTS

The solubility of CC significantly increased by a factor of 27,037.344 when formulated as a solid dispersion matrix using EE100 at a ratio of 1:5 (w/w) drug to polymer (SE-EE5 SD), compared to the solubility of the pure drug. The mechanism of solubility and dissolution rate enhancement of CC by the optimized SDS was found to be via the conversion of the crystalline CC into the amorphous form as well as nanoparticles formation upon dissolution at a pH below 5. The instrumental analysis tests showed good compatibility between CC and EE100 and there was no chemical interaction between the drug and the polymer. Moreover, the stability tests confirmed that the optimized system was stable after three months of storage at 25°C.

CONCLUSION

The utilization of the solid dispersion technique employing EE 100 polymer as a matrix demonstrates significant success in enhancing the solubility, dissolution, and subsequently, the bioavailability of water-insoluble drugs like CC.

Investigating in-vitro functionality and in-vivo taste assessment of eco-friendly Tadalafil Pastilles

Tadalafil (TDL) has poor bioavailability due to the less aqueous solubility and bitter taste. Oral solid dosage forms, especially tablets, have a broad market worldwide. Constraints of tablets are a long process, pollution, high processing cost, and requiring more excipient. The research was performed to optimize an eco-friendly immediate-acting pastille of TDL to put forward an alternate formulation to a tablet using advanced data mining tools. Another objective is to assess the taste masking of TDL using the Brief Access Taste Aversion (BATA) model. The amount of PEG-4000, Polyox N-10, and Kyron T-314 were chosen as critical material attributes from failure mode effect analysis. Box-Behnken design (BBD) was utilized to optimize the pastilles and ascertained the significant impact of chosen variables on disintegration time and % CDR at 10 min. The control strategy and optimal region were located using an overlay plot. The pastilles were able to release the drug within 15 min due to faster disintegration. The formulated pastilles were of uniform size, shape, and mechanical strength. The bitter taste of TDL was masked and confirmed by the BATA model. The newer formulation may be helpful in the industry due to its eco-friendly, single-step, and economical process. It unlocks a new direction in the field of oral solid dosage form as an alternative to tablets.

Oral delivery of posaconazole-loaded phospholipid-based nanoformulation: Preparation and optimization using design of experiments, machine learning, and TOPSIS

Phospholipid-based nanosystems show promising potentials for oral administration of hydrophobic drugs. The study introduced a novel approach to optimize posaconazole-loaded phospholipid-based nanoformulation using the design of experiments, machine learning, and Technique for Order of Preference by Similarity to the Ideal Solution. These approaches were used to investigate the impact of various variables on the encapsulation efficiency (EE), particle size, and polydispersity index (PDI). The optimized formulation, with %EE of ∼ 74 %, demonstrated a particle size and PDI of 107.7 nm and 0.174, respectively. The oral pharmacokinetic profiles of the posaconazole suspension, empty nanoformulation + drug suspension, and drug-loaded nanoformulation were evaluated. The nanoformulation significantly increased maximum plasma concentration and the area under the drug plasma concentration-time curve (∼3.9- and 6.2-fold, respectively) and could be administered without regard to meals. MTT and histopathological examinations were carried out to evaluate the safety of the nanoformulation and results exhibited no significant toxicity. Lymphatic transport was found to be the main mechanism of oral delivery. Caco-2 cell studies demonstrated that the mechanism of delivery was not based on an increase in cellular uptake. Our study represents a promising strategy for the development of phospholipid-based nanoformulations as efficient and safe oral delivery systems.

An evaluation of spectral and statistical parameters of ion pair complexation of Zafirlukast using chromogenic dyes in solid dispersion-based formulations

The purpose of present work was to develop a novel analytical method for orally given leukotriene antagonist Zafirlukast (ZST), present in Meglumine and Eudragit EEPO based solid dispersion formulation. Four simple, extraction-free, fast, and economical methods based on charge transfer complexation among nitrogen of ZST with sulfonyl group comprising chromogenic mediator bromophenol blue (BPB-Method B), bromothymol blue (BTB-Method C) and bromocresol green (BCG-Method D). The first method (A) is based on the analysis using 0.1 M HCl as a solvent at λmax 242 nm while chromogenic methods yield color complex at λmax 415 nm (BPB-Method B), λmax 420 nm (BTB-Method C) and λmax 435 nm (BCG-Method D). The Beer's Law stayed linear in the concentration ranges of 1-10, 10-75, 5-40 and 15-100 μg/ml for methods A, B, C and D, respectively. The spectral and thermodynamic characterization of each method was carried out by the application of Molar Absorptivity, LOD, LOQ, Association Constant and Gibbs free energy (ΔGo). The methods were statistically optimized and evaluated by F-Distribution Value, P-Value, Shapiro-Wilk P-Value, regression analysis, Q-Q plot, prediction interval, residual histogram and plots. Various experimental conditions affecting the complexation and stability of chromogenic complexes are cautiously studied including optimal temperature, chromogenic agent volume, color stability, recovery, precision and accuracy. All the measurements were executed under ICH guidelines. It can be established that proposed would be an appropriate prospective analytical approach for estimation of ZST in pure bulk, solid dispersions and dosage forms.

Utilizing Drug Amorphous Solid Dispersions for the Preparation of Dronedarone per os Formulations

Dronedarone (DRN), an antiarrhythmic drug, exhibits potent pharmacological effects in the management of cardiac arrhythmias. Despite its therapeutic potential, DRN faces formulation challenges due to its low aqueous solubility. Hence, the present study is dedicated to the examination of amorphous solid dispersions (ASDs) as a strategic approach for enhancing the solubility of DRN. Initially, the glass forming ability (GFA) of API was assessed alongside its thermal degradation profile, and it was revealed that DRN is a stable glass former (GFA III compound) that remains thermally stable up to approximately 200 °C. Subsequently, five commonly used ASD matrix/carriers, i.e., hydroxypropyl methylcellulose (HPMC), povidone (PVP), copovidone (PVP/VA), Soluplus® (SOL), and Eudragit® E PO (EPO), were screened for the formation of a DRN-based ASD using film casting and solvent shift methods, along with miscibility evaluation measurements. SOL proved to be the most promising matrix/carrier among the others, and, hence, was used to prepare DRN ASDs via the melt-quench method. The physicochemical characterization of the prepared systems (via pXRD) revealed the complete amorphization of the API within the matrix/carrier, while the system was physically stable for at least three months after its preparation. In vitro release studies for the ASDs, conducted under non-sink conditions, revealed the sustained supersaturation of the drug for at least 8 h. Finally, the use of attenuated total reflectance (ATR) FTIR spectroscopy showed the formation of a strong molecular interaction between the drug molecules and SOL.

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.

Effects of Poloxamers as Excipients on the Physicomechanical Properties, Cellular Biocompatibility, and In Vitro Drug Release of Electrospun Polycaprolactone (PCL) Fibers

Electrospun microfibers are emerging as one of the advanced wound dressing materials for acute and/or chronic wounds, especially with their ability to carry drugs and excipients at a high loading while being able to deliver them in a controlled manner. Various attempts were made to include excipients in electrospun microfibers as wound dressing materials, and one of them is poloxamer, an amphiphilic polymer that exhibits wound debridement characteristics. In this study, we formulated two types of poloxamers (i.e., P188 and P338) at 30% (w/w) loading into electrospun polycaprolactone (PCL) fibers to evaluate their physicomechanical properties, biocompatibility, and in vitro drug release of a model drug. Our findings showed that the incorporation of poloxamers in the PCL solutions during electrospinning resulted in a greater "whipping" process for a larger fiber deposition area. These fibers were mechanically stiffer and stronger, but less ductile as compared to the PCL control fibers. The incorporation of poloxamers into electrospun PCL fibers reduced the surface hydrophobicity of fibers according to our water contact angle studies and in vitro degradation studies. The fibers' mechanical properties returned to those of the PCL control groups after "dumping" the poloxamers. Moreover, poloxamer-loaded PCL fibers accelerated the in vitro release of the model drug due to surface wettability. These poloxamer-loaded PCL fibers were biocompatible, as validated by MTT assays using A549 cells. Overall, we demonstrated the ability to achieve a high loading of poloxamers in electrospun fibers for wound dressing applications. This work provided the basic scientific understanding of materials science and bioengineering with an emphasis on the engineering applications of advanced wound dressings.

Preparation, characterization, and pharmacokinetics of oridonin-loaded liposomes

The aim of this study was to prepare oridonin liposomes and evaluate the physicochemical characteristics and pharmacokinetics in rats. A three-level, three-factor Box-Behnken design was used to optimize the preparation of oridonin liposomes. A highly sensitive high-performance liquid chromatographic quantification method using ultraviolet detection was established and validated for the determination of oridonin in rat plasma. Twelve Sprague-Dawley rats were randomly assigned and injected with 15 mg/kg of oridonin or oridonin liposomes via the tail vein. Pharmacokinetic parameters were estimated using a compartmental modeling approach using PKsolver software. The optimum conditions were as follows: soybean phospholipids/cholesterol ratio, 3.9:1; soybean phospholipids/drug ratio, 8.5:1; and soybean phospholipid concentration, 1.1%. Under these conditions, the mean particle size, polydispersity index, zeta potential, and encapsulation efficiency of oridonin liposomes were 170.5 nm, 0.246, -30.3 mV, and 76.15%, respectively. The pharmacokinetic results showed that liposomes could significantly prolong the elimination half-life (from 2.88 ± 0.55 to 13.67 ± 3.52 h), increase the area under the concentration-time curve (from 1.65 ± 0.17 to 6.22 ± 0.83 μg h/ml), and decrease the clearance (from 6.62 ± 1.38 to 1.96 ± 0.24 L/kg h). The oridonin liposomes increased the elimination half-life and area under the concentration-time curve and provided a reference for the development of drugs with a short half-life.

Formulation Characterization and Pharmacokinetic Evaluation of Amorphous Solid Dispersions of Dasatinib

The aim of this study was to improve the physicochemical properties and oral bioavailability of dasatinib (DST) by the amorphous solid dispersion (ASD) approach using cellulose acetate butyrate (CAB) as a carrier. Various formulations of ASD (DST:CAB 1:1 to 1:5) were prepared by the solvent evaporation method. ASDs were characterized for physicochemical attributes, stability and pharmacokinetics. Scanning electron microscopy, Fourier transformed infrared, X-ray powder diffraction, and differential scanning calorimetry confirmed the transformation of the crystalline drug into amorphous phase. ASD formation resulted in a 3.7−4.9 fold increase in dissolution compared to DST or physical mixture. The ASDs formulation exhibited relative stability against transformation from the unstable amorphous phase to a stable crystalline phase that was indicated by spectral and X-ray powder diffraction data, and insignificant (p > 0.05) decrease in dissolution. Tmax, Cmax and AUC0-∞ of ASD were 4.3-fold faster and 2.0 and 1.5 fold higher than the corresponding physical mixture. In conclusion, the ASD of DST significantly improved dissolution and oral bioavailability which may be translated into a reduction in dose and adverse events.

Atomic Layer Coating to Inhibit Surface Crystallization of Amorphous Pharmaceutical Powders

Preventing crystallization is a primary concern when developing amorphous drug formulations. Recently, atomic layer coatings (ALCs) of aluminum oxide demonstrated crystallization inhibition of high drug loading amorphous solid dispersions (ASDs) for over 2 years. The goal of the current study was to probe the breadth and mechanisms of this exciting finding through multiple drug/polymer model systems, as well as particle and coating attributes. The model ASD systems selected provide for a range of hygroscopicity and chemical functional groups, which may contribute to the crystallization inhibition effect of the ALC coatings. Atomic layer coating was performed to apply a 5-25 nm layer of aluminum oxide or zinc oxide onto ASD particles, which imparted enhanced micromeritic properties, namely, reduced agglomeration and improved powder flowability. ASD particles were stored at 40 °C and a selected relative humidity level between 31 and 75%. Crystallization was monitored by X-ray powder diffraction and scanning electron microscopy (SEM) up to 48 weeks. Crystallization was observable by SEM within 1-2 weeks for all uncoated samples. After ALC, crystallization was effectively delayed or completely inhibited in some systems up to 48 weeks. The delay achieved was demonstrated regardless of polymer hygroscopicity, presence or absence of hydroxyl functional groups in drugs and/or polymers, particle size, or coating properties. The crystallization inhibition effect is attributed primarily to decreased surface molecular mobility. ALC has the potential to be a scalable strategy to enhance the physical stability of ASD systems to enable high drug loading and enhanced robustness to temperature or relative humidity excursions.

New Development in Understanding Drug-Polymer Interactions in Pharmaceutical Amorphous Solid Dispersions from Solid-State Nuclear Magnetic Resonance

Pharmaceutical amorphous solid dispersions (ASDs) represent a widely used technology to increase the bioavailability of active pharmaceutical ingredients (APIs). ASDs are based on an amorphous API dispersed in a polymer, and their stability is driven by the presence of strong intermolecular interactions between these two species (e.g., hydrogen bond, electrostatic interactions, etc.). The understanding of these interactions at the atomic level is therefore crucial, and solid-state nuclear magnetic resonance (NMR) has demonstrated itself as a very powerful technique for probing API-polymer interactions. Other reviews have also reported exciting approaches to study the structures and dynamic properties of ASDs and largely focused on the study of API-polymer miscibility and on the identification of API-polymer interactions. Considering the increased use of NMR in the field, the aim of this Review is to specifically highlight recent experimental strategies used to identify API-polymer interactions and report promising recent examples using one-dimensional (1D) and two-dimensional (2D) experiments by exploiting the following emerging approaches of very-high magnetic field and ultrafast magic angle spinning (MAS). A range of different ASDs spanning APIs and polymers with varied structural motifs is targeted to illustrate new ways to understand the mechanism of stability of ASDs to enable the design of new dispersions.

Data regarding particle size distribution, thermal properties and gaseous phase hydration of co-milled solid dispersions composed of tadalafil and Soluplus

A mechanical activation of the solid particles upon high-energy ball milling may considerably change the physicochemical properties of pharmaceutical compounds, including the morphology, particle size distribution, thermal properties, and surface interactions with water vapour upon gaseous phase hydration. Assessment of these changes is crucial for optimizing the manufacturing process of enabling drug products. In this article, we provide a detailed characterization of binary co-milled solid dispersions composed of tadalafil and Soluplus using a laser diffraction method, differential scanning calorimetry (DSC), gravimetric measurements and solid state ¹H- NMR spectroscopy. The data presented in this article is directly related to our previously published research article. They complement information on the impact that both formulation and process variables may have on the properties of these binary powder formulations.

Coupling AFM, DSC and FT-IR towards Elucidation of Film-Forming Systems Transformation to Dermal Films: A Betamethasone Dipropionate Case Study

Polymeric film-forming systems have emerged as an esthetically acceptable option for targeted, less frequent and controlled dermal drug delivery. However, their dynamic nature (rapid evaporation of solvents leading to the formation of thin films) presents a true characterization challenge. In this study, we tested a tiered characterization approach, leading to more efficient definition of the quality target product profiles of film-forming systems. After assessing a number of physico-chemico-mechanical properties, thermal, spectroscopic and microscopic techniques were introduced. Final confirmation of betamethasone dipropionate-loaded FFS biopharmaceutical properties was sought via an in vitro skin permeation study. A number of applied characterization methods showed complementarity. The sample based on a combination of hydrophobic Eudragit^® RS PO and hydroxypropyl cellulose showed higher viscosity (47.17 ± 3.06 mPa·s) and film thickness, resulting in sustained skin permeation (permeation rate of 0.348 ± 0.157 ng/cm² h), and even the pH of the sample with Eudragit^® NE 30D, along with higher surface roughness and thermal analysis, implied its immediate delivery through the epidermal membrane. Therefore, this study revealed the utility of several methods able to refine the number of needed tests within the final product profile.

Interaction and Compatibility Studies in the Development of Olmesartan Medoxomil and Hydrochlorothiazide Formulations under a Real Manufacturing Process

A drug–drug and drug–excipient interactions and compatibilities study was conducted for two fixed-dose combination (FDC) products containing olmesartan medoxomil (OLM)/hydrochlorothiazide (HCT) 20/12.5 mg and OLM/HCT 40/12.5 mg during their development including storage. The study consisted of the evaluation of samples retrieved during all stages of a real manufacturing process. Powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared spectroscopy (FT-IR), and contact angle techniques were applied to the samples to determine interactions and incompatibilities. Dissolution tests and long-term stability studies were conducted to evaluate dosage form performance. Results showed weak solid–state interactions able to obtain a eutectic mixture of OLM and HCT while microcrystalline cellulose (MC) impacted the thermal stability of both drugs. Reliable dissolution and long-term stability tests confirmed that the interactions observed were not considered incompatibilities because they were not influenced by the performance of the final products.

Pickering Emulsions Stabilized with Curcumin-Based Solid Dispersion Particles as Mayonnaise-like Food Sauce Alternatives

Pickering emulsions, which are emulsions stabilized by colloidal particles, are being increasingly positioned as novel strategies to develop innovative food product solutions. In this context, the present work aims to develop Pickering emulsions stabilized by natural-based curcumin-loaded particles produced by the solid dispersion technique as promising mayonnaise-like food sauce alternatives. Two particle formulations (KC1 and KC2) were produced using k-carrageenan as the matrix material and different curcumin contents, then employed in the preparation of three Pickering emulsion formulations comprising different oil fractions (φ) and particle concentrations (KC1 φ 0.4 (4.7%), KC2 φ 0.4 (4.7%) and KC2 φ 0.6 (4.0%)). The creaming index tests accompanied by the optical microscopy analysis evidenced the good stability of the developed products for the tested period of 28 days. The final products were tested concerning color attributes, pH, oxidative stability, textural, and nutritional composition, and compared with two commercial mayonnaises (traditional and light products). Overall, the produced emulsions were characterized by a bright yellow color (an appealing attribute for consumers), an acidic pH (similar to mayonnaise), and a considerably improved oxidative stability, implying a foreseeable longer shelf life. The sauce KC1 φ 0.4 (4.7%) showed a similar texture to the light commercial mayonnaise, being a promising alternative to conventional sauces, holding a low-fat content and potentially added benefits due to the curcumin and virgin olive oil intrinsic properties.

Formulation and Evaluation of Self-Nanoemulsifying Drug Delivery System Derived Tablet Containing Sertraline

Being a biopharmaceutics classification system class II drug, the absorption of sertraline from the gut is mainly limited by its poor aqueous solubility. The objective of this investigation was to improve the solubility of sertraline utilizing self-nanoemulsifying drug delivery systems (SNEDDS) and developing it into a tablet dosage form. Ternary phase diagrams were created to identify nanoemulsion regions by fixing oil (glycerol triacetate) and water while varying the surfactant (Tween 80) and co-surfactant (PEG 200) ratio (S_mix). A three-factor, two-level (2³) full factorial design (batches F1–F8) was utilized to check the effect of independent variables on dependent variables. Selected SNEDDS (batch F4) was solidified into powder by solid carrier adsorption method and compressed into tablets. The SNEDDS-loaded tablets were characterized for various pharmaceutical properties, drug release and evaluated in vivo in Wistar rats. A larger isotropic region was noticed with a S_mix ratio of 2:1 and the nanoemulsion exhibited good stability. Screening studies’ data established that all three independent factors influence the dependent variables. The prepared tablets displayed optimal pharmaceutical properties within acceptable limits. In vitro sertraline release demonstrated from solid SNEDDS was statistically significant (p < 0.0001) as compared to pure sertraline. Differential Scanning Calorimetry and X-Ray Diffraction data established the amorphous state of the drug in SNEDDS formulation, while FTIR spectra indicate the compatibility of excipients and drug. Pharmacokinetic evaluation of the SNEDDS tablet demonstrated significant increment (p < 0.0001) in AUC_0-α (~5-folds), C_max (~4-folds), and relative bioavailability (386%) as compared to sertraline suspension. The current study concludes that the solid SNEDDS formulation could be a practicable and effective strategy for oral therapy of sertraline.

Recent Advances in the Local Drug Delivery Systems for Improvement of Anticancer Therapy

The conventional anticancer chemotherapies not only cause serious toxic effects, but also produce resistance in tumor cells exposed to long-term therapy. Usually, the killing of metastasized cancer cells requires long-term therapy with higher drug doses, because the cancer cells develop resistance due to the induction of poly-glycoproteins (P-gps) that act as a transmembrane efflux pump to transport drugs out of the cells. During the last few decades, scientists have been exploring new anticancer drug delivery systems such as microencapsulation, hydrogels, and nanotubes to improve bioavailability, reduce drug-dose requirement, decrease multiple drug resistance, and to save normal cells as non-specific targets. Hopefully, the development of novel drug delivery vehicles (nanotubes, liposomes, supramolecules, hydrogels, and micelles) will assist to deliver drug molecules at the specific target site and reduce the undesirable side effects of anticancer therapies in humans. Nanoparticles and lipid formulations are also designed to deliver small drug payload at the desired tumor cell sites for their anticancer actions. This review will focus on the recent advances in the drug delivery systems, and their application in treating different cancer types in humans.

Characterization of Novel Solid Dispersions of Moringa oleifera Leaf Powder Using Thermo-Analytical Techniques

Moringa oleifera leaf powder (MOLP) has been identified as the most important functional ingredient owing to its rich nutritional profile and healthy effects. The solubility and functional properties of this ingredient can be enhanced through solid dispersion technology. This study aimed to investigate the effects of polyethylene glycols (PEGs) 4000 and 6000 as hydrophilic carriers and solid dispersion techniques (freeze-drying, melting, solvent evaporation, and microwave irradiation) on the crystallinity and thermal stability of solid-dispersed Moringa oleifera leaf powders (SDMOLPs). SDMOLPs were dully characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The PXRD results revealed that the solid dispersions were partially amorphous with strong diffraction peaks at 2θ values of 19° and 23°. The calorimetric and thermogravimetric curves showed that PEGs conferred greater stability on the dispersions. The FTIR studyrevealed the existence of strong intermolecular hydrogen bond interactions between MOLP and PEG functional groups. MOLP solid dispersions may be useful in functional foods and beverages and nutraceutical formulations.

Design and Characterization of HY-038 Solid Dispersions via Spray Drying Technology: In Vitro and In Vivo Evaluations

The aim of this study was to prepare HY-038 solid dispersions (SDs) with single carrier at high drug loading and then forming a tablet to enhance solubility, dissolution, and bioavailability via spray drying technology. At the same time, we hope to develop a more convenient in vitro method to predict the absorption behavior of different formulations in vivo. Different solid dispersions, varying in drug/polymer ratios, were prepared. Infrared spectroscopy, differential scanning calorimetry, scanning electron microscope, and X-ray diffraction were used to perform solid-state characterizations of the pure drug and SDs. Contact angle of water, dissolution in pH = 6.8 phosphate buffer, and in vivo absorption in dogs were studied. As a result, solid-state characterization demonstrated the transformation of the crystalline HY-038 to an amorphous state in the solid dispersions, and the in vivo exposure followed with the trend of the dissolution curve combined with contact angle. Compared with the prototype formulation, the C_max and AUC_0-∞ of optimized formulation SD2 (HY-038-HPMCAS 3:1) increased by about 5 ~ 9 times at the same dose. More importantly, the SD2 formulation showed approximately linear increases in C_max and AUC_0-∞ as the dose increased from 50 to 100 mg, while the prototype formulation reached absorption saturation at 50 mg. SD2 (HY-038-HPMCAS 3:1) was selected as the best formulation for the downstream development.

Drug-Polymer Interactions in Acetaminophen/Hydroxypropylmethylcellulose Acetyl Succinate Amorphous Solid Dispersions Revealed by Multidimensional Multinuclear Solid-State NMR Spectroscopy

The bioavailability of insoluble crystalline active pharmaceutical ingredients (APIs) can be enhanced by formulation as amorphous solid dispersions (ASDs). One of the key factors of ASD stabilization is the formation of drug-polymer interactions at the molecular level. Here, we used a range of multidimensional and multinuclear nuclear magnetic resonance (NMR) experiments to identify these interactions in amorphous acetaminophen (paracetamol)/hydroxypropylmethylcellulose acetyl succinate (HPMC-AS) ASDs at various drug loadings. At low drug loading (<20 wt %), we showed that 1H-13C through-space heteronuclear correlation experiments identify proximity between aromatic protons in acetaminophen with cellulose backbone protons in HPMC-AS. We also show that 14N-1H heteronuclear multiple quantum coherence (HMQC) experiments are a powerful approach in probing spatial interactions in amorphous materials and establish the presence of hydrogen bonds (H-bond) between the amide nitrogen of acetaminophen with the cellulose ring methyl protons in these ASDs. In contrast, at higher drug loading (40 wt %), no acetaminophen/HPMC-AS spatial proximity was identified and domains of recrystallization of amorphous acetaminophen into its crystalline form I, the most thermodynamically stable polymorph, and form II are identified. These results provide atomic scale understanding of the interactions in the acetaminophen/HPMC-AS ASD occurring via H-bond interactions.

Drug Amorphous Solid Dispersions Based on Poly(vinyl Alcohol): Evaluating the Effect of Poly(propylene Succinate) as Plasticizer

Although significant actions have been taken towards the utilization of poly(vinyl alcohol) (PVA) in the preparation of drug amorphous solid dispersions (ASDs) using fusion-based techniques (such as melt-quench cooling and hot-melt extrusion), several drawbacks regarding its rather high melting temperature and its thermal degradation profile make the use of the polymer extremely challenging. This is especially important when the active pharmaceutical ingredient (API) has a lower melting temperature (than PVA) or when it is thermally labile. In this vein, a previous study showed that newly synthesized polyester-based plasticizers may improve the processability and the thermal properties of PVA. However, the effects of such polyester-based plasticizers on the drug’s physicochemical and pharmaco-technical properties are yet unknown. Hence, the aim of the present study is to extend our previous findings and evaluate the use of poly(propylene succinate) (PPSu, i.e., the most promising plasticizer in regard to PVA) in the preparation of drug-loaded PVA-based ASDs. Dronedarone (DRN), a poorly water-soluble API, was selected as a model drug, and drug ASDs (using either neat PVA or PVA-PPSu) were prepared using the melt-mixing/quench cooling approach at low melting temperatures (i.e., 170 °C). DSC and pXRD analysis showed that a portion of the API remained crystalline in the ASDs prepared only with the use of neat PVA, while the samples having PPSu as a plasticizer were completely amorphous. Further evaluation with ATR-FTIR spectroscopy revealed the formation of significant intermolecular interactions between the API and the PVA-PPSu matrix, which could explain the system’s physical stability during storage. Finally, dissolution studies, conducted under nonsink conditions, revealed that the use of PVA-PPSu is able to maintain DRN’s sustained supersaturation for up to 8 h.

What Are the Important Factors That Influence API Crystallization in Miscible Amorphous API-Excipient Mixtures during Long-Term Storage in the Glassy State?

In this Perspective, the authors examine the various factors that should be considered when attempting to use miscible amorphous API-excipient mixtures (amorphous solid dispersions and coamorphous systems) to prevent the solid-state crystallization of API molecules when isothermally stored for long periods of time (a year or more) in the glassy state. After presenting an overview of a variety of studies designed to obtain a better understanding of possible mechanisms by which amorphous API undergo physical instability and by which excipients generally appear to inhibit API crystallization from the amorphous state, we examined 78 studies that reported acceptable physical stability of such systems, stored below T_g under "dry" conditions for one year or more. These results were examined more closely in terms of two major contributing factors: the degree to which a reduction in diffusional molecular mobility and API-excipient molecular interactions operates to inhibit crystallization. These two parameters were chosen because the data are readily available in early development to help compare amorphous systems. Since T_g - T = 50 K is often used as a rule of thumb for the establishing the minimum value below T_g required to reduce diffusional mobility to a period of years, it was interesting to observe that 30 of the 78 studies still produced significant physical stability at values of T_g - T < 50 K (3-47 °C), suggesting that factors besides diffusive molecular mobility likely contribute. A closer look at the T_g - T < 50 systems shows that hydrogen bonding, proton transfer, disruption of API-API self-associations (such as dimers), and possible π-π stacking were reported for most of the systems. In contrast, five crystallized systems that were monitored for a year or more were also examined. These systems exhibited T_g - T values of 9-79, with three of them exhibiting T_g - T < 50. For these three samples, none displayed molecular interactions by infrared spectroscopy. A discussion on the impact of relative humidity on long-term crystallization in the glass was included, with attention paid to the relative water vapor sorption by various excipients and effects on diffusive mobility and molecular interactions between API and excipient.

Mutual Effects of Hydrogen Bonding and Polymer Hydrophobicity on Ibuprofen Crystal Inhibition in Solid Dispersions with Poly(N-vinyl pyrrolidone) and Poly(2-oxazolines)

Poly(N-vinyl pyrrolidone) (PVP), poly(2-methyl-2-oxazoline) (PMOZ), poly(2-ethyl-2-oxazoline) (PEOZ), poly(2-n-propyl-2-oxazoline) (PnPOZ), and poly(2-isopropyl-2-oxazoline) (PiPOZ) were used to prepare solid dispersions with ibuprofen (IB), a model poorly-water soluble drug. Dispersions, prepared by solvent evaporation, were investigated using powder X-ray diffractometry, differential scanning calorimetry, and FTIR spectroscopy; hydrogen bonds formed between IB and all polymers in solid dispersions. PMOZ, the most hydrophilic polymer, showed the poorest ability to reduce or inhibit the crystallinity of IB. In contrast, the more hydrophobic polymers PVP, PEOZ, PnPOZ, and PiPOZ provided greater but similar abilities to reduce IB crystallinity, despite the differing polymer hydrophobicity and that PiPOZ is semi-crystalline. These results indicate that crystallinity disruption is predominantly due to hydrogen bonding between the drug molecules and the polymer. However, carrier properties affected drug dissolution, where PnPOZ exhibited lower critical solution temperature that inhibited the release of IB, whereas drug release from other systems was consistent with the degree of ibuprofen crystallinity within the dispersions.

Stability and Influence of Storage Conditions on Nanofibrous Film Containing Tooth Whitening Agent

Carbamide peroxide (CP), a tooth whitening agent, is chemically unstable. The present study explores stability enhancement of CP by loading in a nanofibrous film (CP-F) composed of polyvinyl alcohol/polyvinylpyrrolidone/silica mixture, using an electrospinning technique. Kept at a temperature range of 60–80 °C for 6 h, CP in CP-F showed significantly higher stability than that in a polymer solution and in water, respectively. Degradation of CP in CP-F could be described by the first order kinetics with the predicted half-life by the Arrhenius equation of approximately 6.52 years. Physicochemical properties of CP-F after long-term storage for 12 months at different temperatures and relative humidity (RH) were investigated using scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and Fourier transform infrared spectroscopy. It was found that high temperature and high humidity (45 °C/75% RH) could enhance water absorption and destruction of the nanofibrous structure of CP-F. Interestingly, kept at 25 °C/30% RH, the nanofibrous structure of CP-F was not damaged, and exhibited no water absorption. Moreover, the remaining CP, the mechanical properties, and the adhesive properties of CP-F were not significantly changed in this storage condition. It is concluded that the developed CP-F and a suitable storage condition can significantly improve CP stability.