The effects of pH, surfactant, ion concentration, coformer, and molecular arrangement on the solubility behavior of myricetin cocrystals

Two Novel Hydrate Salts of Norfloxacin with Phenolic Acids and Their Physicochemical Properties

Norfloxacin (NORF) is a broad-spectrum quinolone that is widely utilized for the treatment of various bacterial infections and is considered one of the most commonly used fluoroquinolone antibiotics. However, NORF's clinical utility is limited by its poor water solubility and relatively low oral bioavailability. This study presents an optimization and synergistic enhancement approach through salt/co-crystal, aiming to maximize the biopharmaceutical properties of NORF with the use of phenolic acid. Following this strategy, two new hydrate salts of NORF with phenolic acid, namely, NORF-3,5-DBA hydrate (salt 1) and NORF-VA hydrate (salt 2), were prepared and systematically confirmed. Two hydrate salts were produced by means of the slow evaporation crystallization method, and the structures were determined through single-crystal X-ray diffraction (SCXRD). Additionally, powder X-ray diffraction (PXRD), Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and high-performance liquid chromatography (HPLC) were applied to analyze the features of the two salts. The experimental results indicated that the formation of the two salts could enhance the solubility and improve the release behavior of NORF. Interestingly, the physicochemical properties of NORF were significantly improved as a result, leading to an enhancement in its antibacterial activity. This was demonstrated by the enhanced inhibition of bacterial strains and the lower minimum inhibitory concentration values.

Exploratory Investigation of Zinc-Modified Borosilicate Bioactive Glass: A New Methodology for Its Biocompatibility, Immunoregulation, and Pro-Angiogenic Property Evaluation

The assessment of biodegradable materials, such as bioactive glass, under the existing ISO 10993 standard test methods poses a significant challenge due to potential cell viability impairment caused by the accumulation of degraded products in a static environment. Therefore, innovative methodologies are urgently needed to tailor the unique biodegradation characteristics of these materials, providing more precise and scientific insights into biosafety and efficacy verification. Motivation by its bidirectional regulation of angiogenesis and immunity, zinc (Zn) was incorporated into sol-gel-derived borosilicate bioactive glasses (SBSGs) to fabricate Zn-incorporated borosilicate bioactive glasses (SBSG-Zn) to complement the tissue repair capabilities of bioactive glasses. Both SBSG and SBSG-Zn glasses consist of nanosized particles, slit mesoporous pores, high specific surface areas, and bioreactivity. In vitro comparative analysis, conducted according to ISO 10993 standards, demonstrates that only at suitable dilution rates─such as the 8-fold dilution employed in this study─do extracts of SBSG and SBSG-Zn glasses exhibit low cytotoxicity when cultured with human umbilical vein endothelial cells (HUVECs). Notably, SBSG-Zn glasses show optimal promotion of angiogenic gene expression in HUVECs. Furthermore, within an appropriate concentration range of released ions, SBSG-Zn glass extracts not only promote cell survival but also modulate the expression of anti-inflammatory genes while simultaneously inhibiting pro-inflammatory genes concurrently. After being implanted in rat subcutaneous defect models, both SBSG and SBSG-Zn glasses demonstrated the local immunoregulation and angiogenic effects. SBSG-Zn stands out by demonstrating superior modulation of M1/M2 polarization in macrophages as validated by altered secretion of key factors in macrophages and expression of relevant growth factors in HUVECs. These findings underscore the potential for convenient manipulation of localized angiogenic and immunoregulation through the incorporation of zinc into bioactive glass, emphasizing the importance of ensuring the appropriate ion doses are applied for achieving optimal therapeutic efficiency.

Comparative Analysis of Fluorescence Emission in Myricetin, Kaempferol, and Quercetin Powders and Solutions

Myricetin is a flavonol with high antioxidant properties. In this research, the fluorescence emission of myricetin powder and its solutions in different solvents were measured and analyzed by comparing with the results of calculations. Comparison of the calculated and measured characteristic wavelengths allowed the identification of all the spectral features in the fluorescence spectra of myricetin powder and solutions with different concentrations. The computation was based on modeling the process of the excited state intermolecular proton transfer, which predicts the formation of tautomeric forms of the flavonol molecule. Characteristic emission wavelengths were obtained using TDDFT/M06-2X/6-31++G(d,p). To understand the influence of the hydroxyl groups in the B-ring of the flavonol molecule on the emission spectrum, we also compared the fluorescence spectra of myricetin with those of kaempferol and quercetin. Moreover, based on the analysis of the changes in the shape of the FL spectra with the concentration of the solution, a criterion for the complete dissolution of the flavonol powders was established, which is important for bioavailability of flavonoids.

The Bioavailability of Drugs-The Current State of Knowledge

Drug bioavailability is a crucial aspect of pharmacology, affecting the effectiveness of drug therapy. Understanding how drugs are absorbed, distributed, metabolized, and eliminated in patients' bodies is essential to ensure proper and safe treatment. This publication aims to highlight the relevance of drug bioavailability research and its importance in therapy. In addition to biochemical activity, bioavailability also plays a critical role in achieving the desired therapeutic effects. This may seem obvious, but it is worth noting that a drug can only produce the expected effect if the proper level of concentration can be achieved at the desired point in a patient's body. Given the differences between patients, drug dosages, and administration forms, understanding and controlling bioavailability has become a priority in pharmacology. This publication discusses the basic concepts of bioavailability and the factors affecting it. We also looked at various methods of assessing bioavailability, both in the laboratory and in the clinic. Notably, the introduction of new technologies and tools in this field is vital to achieve advances in drug bioavailability research. This publication also discusses cases of drugs with poorly described bioavailability, providing a deeper understanding of the complex challenges they pose to medical researchers and practitioners. Simultaneously, the article focuses on the perspectives and trends that may shape the future of research regarding bioavailability, which is crucial to the development of modern pharmacology and drug therapy. In this context, the publication offers an essential, meaningful contribution toward understanding and highlighting bioavailability's role in reliable patient treatment. The text also identifies areas that require further research and exploration.

Current research trends of nanomedicines

Owing to the inherent shortcomings of traditional therapeutic drugs in terms of inadequate therapeutic efficacy and toxicity in clinical treatment, nanomedicine designs have received widespread attention with significantly improved efficacy and reduced non-target side effects. Nanomedicines hold tremendous theranostic potential for treating, monitoring, diagnosing, and controlling various diseases and are attracting an unfathomable amount of input of research resources. Against the backdrop of an exponentially growing number of publications, it is imperative to help the audience get a panorama image of the research activities in the field of nanomedicines. Herein, this review elaborates on the development trends of nanomedicines, emerging nanocarriers, in vivo fate and safety of nanomedicines, and their extensive applications. Moreover, the potential challenges and the obstacles hindering the clinical translation of nanomedicines are also discussed. The elaboration on various aspects of the research trends of nanomedicines may help enlighten the readers and set the route for future endeavors.

Enhancing Solubility and Dissolution Rate of Antifungal Drug Ketoconazole through Crystal Engineering

To improve the solubility and dissolution rate of the BCS class II drug ketoconazole, five novel solid forms in 1:1 stoichiometry were obtained upon liquid-assisted grinding, slurry, and slow evaporation methods in the presence of coformers, namely, glutaric, vanillic, 2,6-dihydroxybenzoic, protocatechuic, and 3,5-dinitrobenzoic acids. Single-crystal X-ray diffraction analysis revealed that the hydroxyl/carboxylic acid. . .N-imidazole motif acts as the dominant supramolecular interaction in the obtained solid forms. The solubility of ketoconazole in distilled water significantly increased from 1.2 to 2165.6, 321.6, 139.1, 386.3, and 191.7 μg mL-1 in the synthesized multi-component forms with glutaric, vanillic, 2,6-dihydroxybenzoic, protocatechuic, and 3,5-dinitrobenzoic acid, respectively. In particular, the cocrystal form with glutaric acid showed an 1800-fold solubility increase in water concerning ketoconazole. Our study provides an alternative approach to improve the solubility and modify the release profile of poorly water-soluble drugs such as ketoconazole.

Recent Advances in Pharmaceutical Cocrystals: A Focused Review of Flavonoid Cocrystals

Cocrystallization is currently an attractive technique for tailoring the physicochemical properties of active pharmaceutical ingredients (APIs). Flavonoids are a large class of natural products with a wide range of beneficial properties, including anticancer, anti-inflammatory, antiviral and antioxidant properties, which makes them extensively studied. In order to improve the properties of flavonoids, such as solubility and bioavailability, the formation of cocrystals may be a feasible strategy. This review discusses in detail the possible hydrogen bond sites in the structure of APIs and the hydrogen bonding networks in the cocrystal structures, which will be beneficial for the targeted synthesis of flavonoid cocrystals. In addition, some successful studies that favorably alter the physicochemical properties of APIs through cocrystallization with coformers are also highlighted here. In addition to improving the solubility and bioavailability of flavonoids in most cases, flavonoid cocrystals may also alter their other properties, such as anti-inflammatory activity and photoluminescence properties.

Recent Advances in Pharmaceutical Cocrystals: From Bench to Market

The pharmacokinetics profile of active pharmaceutical ingredients (APIs) in the solid pharmaceutical dosage forms is largely dependent on the solid-state characteristics of the chemicals to understand the physicochemical properties by particle size, size distribution, surface area, solubility, stability, porosity, thermal properties, etc. The formation of salts, solvates, and polymorphs are the conventional strategies for altering the solid characteristics of pharmaceutical compounds, but they have their own limitations. Cocrystallization approach was established as an alternative method for tuning the solubility, permeability, and processability of APIs by introducing another compatible molecule/s into the crystal structure without affecting its therapeutic efficacy to successfully develop the formulation with the desired pharmacokinetic profile. In the present review, we have grossly focused on cocrystallization, particularly at different stages of development, from design to production. Furthermore, we have also discussed regulatory guidelines for pharmaceutical industries and challenges associated with the design, development and production of pharmaceutical cocrystals with commercially available cocrystal-based products.

Amino Acids as the Potential Co-Former for Co-Crystal Development: A Review

Co-crystals are one of the most popular ways to modify the physicochemical properties of active pharmaceutical ingredients (API) without changing pharmacological activity through non-covalent interactions with one or more co-formers. A "green method" has recently prompted many researchers to develop solvent-free techniques or minimize solvents for arranging the eco-friendlier process of co-crystallization. Researchers have also been looking for less-risk co-formers that produce the desired API's physicochemical properties. This review purposed to collect the report studies of amino acids as the safe co-former and explored their advantages. Structurally, amino acids are promising co-former candidates as they have functional groups that can form hydrogen bonds and increase stability through zwitterionic moieties, which support strong interactions. The co-crystals and deep eutectic solvent yielded from this natural compound have been proven to improve pharmaceutical performance. For example, l-glutamine could reduce the side effects of mesalamine through an acid-base stabilizing effect in the gastrointestinal fluid. In addition, some amino acids, especially l-proline, enhances API's solubility and absorption in its natural deep eutectic solvent and co-crystals systems. Moreover, some ionic co-crystals of amino acids have also been designed to increase chiral resolution. Therefore, amino acids are safe potential co-formers, which are suitable for improving the physicochemical properties of API and prospective to be developed further in the dosage formula and solid-state syntheses.

Cocrystal of Apixaban-Quercetin: Improving Solubility and Bioavailability of Drug Combination of Two Poorly Soluble Drugs

Drug combinations have been the hotspot of the pharmaceutical industry, but the promising applications are limited by the unmet solubility and low bioavailability. In this work, novel cocrystals, consisting of two antithrombotic drugs with poor solubility and low bioavailability in vivo, namely, apixaban (Apx) and quercetin (Que), were developed to discover a potential method to improve the poor solubility and internal absorption of the drug combination. Compared with Apx, the dissolution behavior of Apx–Que (1:1) and Apx–Que–2ACN (1:1:2) was enhanced significantly, while the physical mixture of the chemicals failed to exhibit the advantages. The dissolution improvements of Apx–Que–2ACN could be explained by the fact that the solid dispersion-like structure and column-shaped cage of Que accelerated the access of the solvent to the inner layer of Apx. The fracture of the hydrogen bonds of Apx, which was the joint of the adjacent Que chains, facilitated the break-up of the structures. Besides, the bioavailability of Apx–Que was increased compared with the physical mixture and Apx, and Apx–Que remained stable in high temperature and illumination conditions. Therefore, a drug–drug cocrystal of two antithrombotic agents with poor solubility was developed, which exhibited greatly improved solubility, bioavailability and superior stability, indicating a novel method to overcome the shortages of drug combination.

Physicomechanical, stability, and pharmacokinetic evaluation of aceclofenac dimethyl urea cocrystals

Poor physicomechanical properties and limited aqueous solubility restrict the bioavailability of aceclofenac when given orally. To improve its above properties, aceclofenac (ACE) was cocrystallized with dimethyl urea (DMU) in 1:2 molar ratio by dry and solvent assisted grinding. The cocrystals were characterized by ATR-FTIR, DSC, and PXRD, and their surface morphology was studied by SEM. There was enhancement in intrinsic dissolution rate (IDR) (~eight- and ~fivefold in cocrystals prepared by solvent assisted grinding (SAG) and solid state grinding (SSG), respectively, in 0.1 N HCl, pH 1.2) and similarly (~3.42-fold and ~1.20-fold in phosphate buffer, pH 7.4) as compared to pure drug. Additionally, mechanical properties were assessed by tabletability curves. The tensile strength of ACE was < 1 MPa in contrast to the cocrystal tensile strength (3.5 MPa) which was ~1.98 times higher at 6000 psi. The tablet formulation of cocrystal by direct compression displayed enhanced dissolution profile (~36% in 0.1 N HCl, pH 1.2, and ~100% in phosphate buffer, pH 7.4) in comparison to physical mixture (~ 30% and ~ 80%) and ACE (~18% and ~50%) after 60 min, respectively. Stability studies of cocrystal tablets for 3 months indicated a stable formulation. Pharmacokinetic studies were performed by using rabbit model. The AUC_0-∞ (37.87±1.3 μgh/ml) and C_max (6.94±2.94 μg/ml) of the selected cocrystal C1 prepared by SAG were significantly enhanced (p < 0.05) and were ~3.43 and ~1.63-fold higher than that of ACE. In conclusion, new cocrystal of ACE-DMU was successfully prepared with improved tabletability, in vitro and in vivo properties.

New insight into improving the solubility of poorly soluble drugs by preventing the formation of their hydrogen-bonds: a case of dapsone salts with camphorsulfonic and 5-sulfosalicylic acid

The improved solubility of two salts of dapsone (DAP) was investigated from the view point of structures and hydrogen bonding.

A Novel Co-Crystal of Bexarotene and Ligustrazine Improves Pharmacokinetics and Tissue Distribution of Bexarotene in SD Rats

Bexarotene (BEX), a specific retinoic acid X receptor (RXR) agonist granted by Food and Drug Administration (FDA) approval for the clinical treatment of T cell lymphoma, has now been found to exert pharmacological effects in the nervous system, with low bioavailability and poor cerebral distribution limiting its application in treatment on neurological disorders. Pharmaceutical co-crystal was a helpful method to improve the bioavailability and tissue distribution of active pharmaceutical ingredients (APIs). Here, 2bexarotene-ligustrazine (2BEX-LIG), a novel co-crystal system of BEX and ligustrazine (LIG) of which with BEX is an API, was constructed with satisfactory stability and enhanced solubility. The pharmacokinetics characteristics of BEX were detected, and the results showed that the absolute bioavailability and the cerebral concentration of BEX in rats administrated with 2BEX-LIG were enhanced from 22.89% to 42.86% and increased by 3.4-fold, respectively, compared with those in rats administrated an equivalent of BEX. Hence, our present study indicated that the novel co-crystal of 2BEX-LIG contributed to improving BEX oral bioavailability and cerebral distribution, thereby providing significant advantages for clinical application of brain tumors and other neurological diseases.

Pharmaceutical cocrystal: a game changing approach for the administration of old drugs in new crystalline form

Pharmaceutical cocrystals are still gaining the interest of the researchers due to their potential to alter physicochemical, mechanical, and pharmacokinetic properties of active pharmaceutical ingredients without negotiating therapeutic action. The diverse new applications of cocrystals, like taste masking, reduced toxicity, patenting opportunities, commercial potential, etc. act as driving force to the rising interest of the pharmaceutical industries. Initially, cocrystals from the view of regulatory authorities, design strategies, cocrystal preparation in brief with special emphasis on scalable and solvent-free hot melt extrusion method, and practical guide to characterization have been provided. The special focus has been given to the biopharmaceutical attributes of the cocrystal. Finally, challenges before and after cocrystal preparation are presented in this review along with some commercial examples of the cocrystals.

Salt Cocrystal of Diclofenac Sodium-L-Proline: Structural, Pseudopolymorphism, and Pharmaceutics Performance Study

Previously, we have reported on a zwitterionic cocrystal of diclofenac acid and L-proline. However, the solubility of this multicomponent crystal was still lower than that of diclofenac sodium salt. Therefore, this study aimed to observe whether a multicomponent crystal could be produced from diclofenac sodium hydrate with the same coformer, L-proline, which was expected to improve the pharmaceutics performance. Methods involved screening, solid phase characterization, structure determination, stability, and in vitro pharmaceutical performance tests. First, a phase diagram screen was carried out to identify the molar ratio of the multicomponent crystal formation. Next, the single crystals were prepared by slow evaporation under two conditions, which yielded two forms: one was a rod-shape and the second was a flat-square form. The characterization by infrared spectroscopy, thermal analysis, and diffractometry confirmed the formation of the new phases. Finally, structural determination using single crystal X-ray diffraction analysis solved the new salt cocrystals as a stable diclofenac-sodium-proline-water (1:1:1:4) named NDPT (natrium diclofenac proline tetrahydrate), and unstable diclofenac-sodium-proline-water (1:1:1:1), named NDPM (natrium diclofenac proline monohydrate). The solubility and dissolution rate of these multicomponent crystals were superior to those of diclofenac sodium alone. The experimental results that this salt cocrystal is suitable for further development.

Polymorphs and pharmacokinetics of an antipsychotic drug candidate

A potent antipsychotic drug candidate, 7-(4-(4-(6-fluorobenzo[d]-isoxazol-3-yl)-piperidin-1-yl)butoxy)-4-methyl-8-chloro -2H-chromen-2-one mesylate(CY611), with good in vitro and in vivo antipsychotic effects was investigated for preformulation evaluation by crystallography methods. Three anhydrous polymorphs(Form I-III), a monohydrate(Form IV), and a NMP solvate(Form V) were discovered and characterized by powder X-ray diffraction, thermal analysis, attenuated total reflection-fourier transform infrared spectroscopy and scanning electron microscopy. Form I, monohydrate Form IV, and a NMP solvate Form V of the drug candidate were isolated, and their structures were determined by single crystal X-ray diffraction. IDR and relative stability experiment were performed. Although Form II has the fastest release rate in water, it easy transformed to monohydrate which has the lowest release rate. In vivo pharmacokinetic study showed that the Form III has the highest bioavailability at 35.4%. Considering the balance between the physicochemical properties, bioavailability and manufacturability of the available polymorphs, Form III may be the optimal form candidate for the eventual formulation.

Development of a dissolution method for lumefantrine and artemether in immediate release fixed dose artemether/lumefantrine tablets

Background

Dissolution of artemether (ART) and lumefantrine (LUM) active pharmaceutical ingredients (APIs) in fixed dose combination (FDC) ART/LUM tablets is one of the critical quality attributes. Thus, the verification of the release profile of ART and LUM from FDC ART/LUM tablets using a robust and discriminatory dissolution method is crucial. Therefore, the aim of this study was to develop and validate an appropriate dissolution method for quality control of FDC ART/LUM tablets.

Methods

The dissolution medium was selected based on saturation solubility data and sink conditions. The effect of agitation speed, pH and surfactant concentration on the release of ART and LUM was evaluated by employing a two-level factorial experiment. The resulting final method was validated for linearity, precision, robustness and API stability. In addition, the discriminatory power of the method was evaluated using expired and unexpired FDC ART/LUM products.

Results

A suitable dissolution profile of FDC ART/LUM tablets was obtained in 900 ml HCl (0.025 N, pH 1.6) with 1%Myrj 52 using paddle method at 100 rpm and 37 °C. ART and LUM were analysed using a HPLC method with UV detection at wavelengths of 210 and 335 nm, respectively. The results from the stability study showed that ART and LUM were sufficiently stable in HCl (0.025 N, pH 1.6) with 1%Myrj 52 at 37 °C. The method was linear (r² = 0.999) over the concentration range of 6.25–100 μg/ml. The results for precision were within the acceptance limit (%RSD < 2). The percent relative standard deviation (< 2%) and statistically non-significant (p > 0.05) difference in release of ART and LUM observed between deliberately changed dissolution method settings (pH = 1.6 ± 0.2 or agitation speed = 100 ± 2) and optimized dissolution conditions revealed the robustness of the dissolution method. The method was capable to discriminate among different FDC ART/LUM products with different quality.

Conclusions

The developed dissolution method is robust and discriminatory. It can be used in the quality evaluation of FDC ART/LUM tablets.

Pharmaceutical Co-Crystallization: Regulatory Aspects, Design, Characterization, and Applications

Pharmaceutical co-crystals are novel class of pharmaceutical substances, which possess an apparent probability of advancement of polished physical properties offering stable and patentable solid forms. These multi-component crystalline forms influence pertinent physicochemical parameters like solubility, dissolution rate, chemical stability, physical stability, etc. which in turn result in the materials with superior properties to those of the free drug. Co-crystallization is a process by which the molecular interactions can be altered to optimize the drug properties. Co-crystals comprise a multicomponent system of active pharmaceutical ingredient (API) with a stoichiometric amount of a pharmaceutically acceptable coformer incorporated in the crystal lattice. By manufacturing pharmaceutical co-crystals, the physicochemical properties of a drug can be improved thus multicomponent crystalline materials have received renewed interest in the current scenario due to the easy administration in the pharmaceutical industry. There is an immense amount of literature available on co-crystals. However, there is a lack of an exhaustive review on a selection of coformers and regulations on co-crystals. The review has made an attempt to bridge this gap. The review also describes the methods used to prepare co-crystals with their characterization. Brief description on the pharmaceutical applications of co-crystals has also been incorporated here. Efforts are made to include reported works on co-crystals, which further help to understand the concept of co-crystals in depth.

Hydrophobically Modified Glucan as an Amphiphilic Carbohydrate Polymer for Micellar Delivery of Myricetin

Myricetin (Myr) is a phytochemical with many functional properties. However, its hydrophobicity, low bioavailability, and stability limit its application. In this study, octadecanoate oat β-glucan (OGE) was synthesized and gained recognition as a self-assembled micelle forming a polymer with a critical micelle concentration (CMC) of 59.4 μg/mL. The Myr-loaded OGE micelle was then prepared and characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Fourier-transform infrared spectroscopy (FT-IR) spectra. The water solubility of Myr was greatly enhanced by forming the Myr/OGE inclusion complex. Consequently, compared to free Myr, the retention of Myr in Myr-loaded OGE micelle was effectively increased during the intestinal digestion phase, and its antioxidant activity was also improved. Overall, our findings demonstrated the potential applications of OGE polymer for the development of prospective micelle in health food, cosmetics, and pharmaceutical fields because they can aid in the delivery of hydrophobic functional compounds like Myr.

Role of Structure, Microenvironmental pH, and Speciation To Understand the Formation and Properties of Febuxostat Eutectics

Cocrystallization studies were undertaken to improve the solubility of a highly water-insoluble drug, febuxostat (FXT), used in the treatment of gout and hyperuricemia. A liquid-assisted grinding (LAG) method was successfully employed, starting with the screening of various coformers for obtaining cocrystals. However, in this process, three eutectic systems with coformers (probenecid, adipic acid, and α-ketoglutaric acid) were formed. Affinities of the different functional groups to form a hydrogen bond and ΔpK_a differences, leading to the eutectic formation, were discussed. The eutectic systems thus formed were further characterized and analyzed using a differential scanning calorimeter (DSC) and powder X-ray diffraction (PXRD). Binary thermal phase diagrams were plotted using different ratios of the systems to confirm the formation of eutectics, and pH-dependent solubility studies exhibited a significant decrease in the solubility in comparison to that of the drug for all three eutectic systems. The solubility of FXT reduced from 46.53 μg/mL (pH 5.63) to 46.03 μg/mL, 28.53 μg/mL, and 18.88 μg/mL; 770.58 μg/mL (pH 8.21) to 307.574 μg/mL, 116.63 μg/mL, 113.40 μg/mL; and from 13165.97 μg/mL (pH 10.13) to 1409.737 μg/mL, 854.51 μg/mL, and 1218.99 μg/mL for FXT-probenecid, FXT-adipic acid, and FXT-α-ketoglutaric acid eutectic systems, respectively. Furthermore, the microenvironmental pH studies were carried out to understand the effect of the microenvironment on the solubility of these eutectic systems. The contribution to solubility from lattice and nonlattice forces considering the microenvironment was also discussed.