Incorporation of Complexation into a Coamorphous System Dramatically Enhances Dissolution and Eliminates Gelation of Amorphous Lurasidone Hydrochloride

Nucleotides as new co-formers in co-amorphous systems: Enhanced dissolution rate, water solubility and physical stability

Developing co-amorphous systems is an attractive strategy to improve the dissolution rate of poorly water-soluble drugs. Various co-formers have been investigated. However, previous studies revealed that it is a challenge to develop satisfied acidic co-formers, e.g., acidic amino acids showed much poorer co-former properties than neutral and basic amino acids. Only a few acidic co-formers have been reported, such as aspartic acid, glutamic acid, and some other organic acids. Thus, this study aims to explore the possibility of adenosine monophosphate and adenosine diphosphate used as acidic co-formers. Mebendazole, celecoxib and tadalafil were used as the model drugs. The drug-co-former co-amorphous systems were prepared via ball milling and confirmed using XRPD. The dissolution study suggested that the solubility and dissolution rate of the drug-co-formers systems were increased significantly compared to the corresponding crystalline and amorphous drugs. The stability study revealed that using the two nucleotides as co-formers enhanced the physical stability of pure amorphous drugs. Molecular interactions were observed in MEB-co-former and TAD-co-former systems and positively affected the pharmaceutical performance of the investigated co-amorphous systems. In conclusion, the two nucleotides could be promising potential acidic co-formers for co-amorphous systems.

Counter-intuitive discovery in the formulation of poorly water-soluble drugs: Amorphous small-molecule gels

Amorphous strategies have been extensively used in improving the dissolution of insoluble drugs for decades due to their high free energy. However, the formation of amorphous small-molecule gels (ASMGs) presents a counter-intuitive discovery that significantly limits their practical application. Recently, ASMGs have garnered attention because of their noncovalent structures, excellent biodegradability, and significant potential in various drug delivery systems in the pharmaceutical field. Hence, a comprehensive review is necessary to contribute to a better understanding of recent advances in ASMGs. This review aimed to introduce the main formation mechanisms, summarize possible influencing factors, generalize unique properties, outline elimination strategies, and discuss clinical application potential with preclinical cases of ASMGs. Moreover, few ASMGs are advanced to clinical stages. Intensive clinical research is needed for further development. We hope that this review can provide more efficient and rational guidance for exploring further clinical applications of ASMGs.

Functional in situ formed deep eutectic solvents improving mechanical properties of powders by enhancing interfacial interactions

As novel green solvents, deep eutectic solvent (DES) with distinct liquid properties has gained increasing interest in pharmaceutical fields. In this study, DES was firstly utilized for improving powder mechanical properties and tabletability of drugs, and the interfacial interaction mechanism was explored. Honokiol (HON), a natural bioactive compound, was used as model drug, and two novel HON-based DESs were synthesized with choline chloride (ChCl) and l-menthol (Men), respectively. The extensive non-covalent interactions were account for DES formation according to FTIR, ¹H NMR and DFT calculation. PLM, DSC and solid-liquid phase diagram revealed that DES successfully in situ formed in HON powders, and the introduction of trace amount DES (99:1 w/w for HON-ChCl, 98:2 w/w for HON-Men) significantly improve mechanical properties of HON. Surface energy analysis and molecular simulation revealed that the introduced DES promoted the formation of solid-liquid interfaces and generation of polar interactions, which increase interparticulate interactions, thus better tabletability. Compared to nonionic HON-Men DES, ionic HON-ChCl DES exhibited better improvement effect, since their more hydrogen-bonding interactions and higher viscosity promote stronger interfacial interactions and adhesion effect. The current study provides a brand-new green strategy for improving powder mechanical properties and fills in the blank of DES application in pharmaceutical industry.

Complexation of Apigenin and Oxymatrine Leading to Enhanced Anti-inflammatory Activity

Apigenin (APG) is a well-known dietary flavonoid with multiple bioactivities, but its poor aqueous solubility may result in low oral bioavailability and thus compromised therapeutic effects. In the present study, APG was complexed with oxymatrine (OMT), a natural quinolizidine alkaloid, for enhanced anti-inflammatory activity, and the related mechanisms in the interaction of APG with OMT were investigated. Fourier transform-infrared spectroscopy, fluorescence spectroscopy, Raman spectroscopy, and proton nuclear magnetic resonance spectroscopy characterizations demonstrated the occurrence of an APG-OMT complex formed at a molar ratio of 1:2. Then, molecular dynamics simulations and quantum chemical calculations were utilized to elucidate that hydrogen bonding, van der Waals forces, and hydrophobic effects were the main forces acting in the formation of the APG-OMT complex. Pharmacokinetic studies in rats demonstrated that the oral bioavailability of APG in the APG-OMT complex was significantly higher than that of APG alone. Finally, bioactivity evaluation in the lipopolysaccharide-induced acute inflammatory injury mouse models showed that the APG-OMT complex exhibited more potent anti-inflammatory effects than APG alone. This study confirmed that APG and OMT exerted enhanced anti-inflammatory effects through self-complexation, which may provide a novel strategy for improving the bioavailability and bioactivity of natural product mixtures.

Tranilast-matrine co-amorphous system: Strong intermolecular interactions, improved solubility, and physiochemical stability

There is a great interest to develop co-amorphous drug delivery systems to enhance the solubility of biopharmaceutics classification system (BCS) class II and IV drugs. However, most reported systems only resulted in severalfold solubility improvement. Tranilast (TRA) is an anti-allergic drug used to treat bronchial asthma and allergic rhinitis. It is a BCS class II drug and its poor aqueous solubility affects its absorption in vivo. To address this issue, a natural alkaloid matrine (MAR) with interesting biological activities was chosen to form a co-amorphous system with TRA, based on the solubility parameter and phase solubility experiment. The TRA-MAR drug-drug co-amorphous system was prepared by the solvent evaporation method, and further characterized by powder X-ray diffraction and modulated temperature differential scanning calorimetry. Fourier transform infrared spectroscopy, FT-Raman, and X-ray photoelectron spectroscopy revealed the formation of salt and the presence of strong intermolecular interactions in the TRA-MAR co-amorphous system, which are also supported by molecular dynamics simulations, showing ionic and hydrogen bonding interactions. This co-amorphous system exhibited excellent physical stability at both 25 °C and 40 °C under anhydrous silica gel condition. Finally, co-amorphous TRA-MAR showed greatly enhanced solubility (greater than 100-fold) and rapid release behavior in the vitro release experiments. NMR spectroscopy revealed the strong intermolecular interactions between TRA and MAR in both DMSO‑d₆ and D₂O. Our study resulted in a TRA-MAR co-amorphous drug system with significant solubility improvement and showcased the great potential to improve the dissolution behaviors of BCS class II and IV drugs through the co-amorphization approach.

Improving Lurasidone Hydrochloride's Solubility and Stability by Higher-Order Complex Formation with Hydroxypropyl-β-cyclodextrin

The biopharmaceutical classification system groups low-solubility drugs into two groups: II and IV, with high and low permeability, respectively. Most of the new drugs developed for common pathologies present solubility issues. This is the case of lurasidone hydrochloride-a drug used for the treatment of schizophrenia and bipolar depression. Likewise, the stability problems of some drugs limit the possibility of preparing them in liquid pharmaceutical forms where hydrolysis and oxidation reactions can be favored. Lurasidone hydrochloride presents the isoindole-1,3-dione ring, which is highly susceptible to alkaline hydrolysis, and the benzisothiazole ring, which is susceptible to a lesser extent to oxidation. Herein, we propose to study the increase in the solubility and stability of lurasidone hydrochloride by the formation of higher-order inclusion complexes with hydroxypropyl-β-cyclodextrin. Several stoichiometric relationships were studied at between 0.5 and 3 hydroxypropyl-β-cyclodextrin molecules per drug molecule. The obtained products were characterized, and their solubility and stability were assessed. According to the obtained results, the formation of inclusion complexes dramatically increased the solubility of the drug, and this increased with the increase in the inclusion ratio. This was associated with the loss of crystalline state of the drug, which was in an amorphous state according to infrared spectroscopy, calorimetry, and X-ray analysis. This was also correlated with the stabilization of lurasidone by the cyclodextrin inhibiting its recrystallization. Phase solubility,¹H-NMR, and docking computational characterization suggested that the main stoichiometric ratio was 1:1; however, we cannot rule out a 1:2 ratio, where a second cyclodextrin molecule could bind through the isoindole-1,3-dione ring, improving its stability as well. Finally, we can conclude that the formation of higher-order inclusion complexes of lurasidone with hydroxypropyl-β-cyclodextrin is a successful strategy to increase the solubility and stability of the drug.

Recrystallization Mediates the Gelation of Amorphous Drugs: The Case of Acemetacin

Amorphization is widely used as an effective method of increasing the solubility of insoluble drugs. However, some amorphous drugs exhibit a much lower dissolution rate than their corresponding crystalline form due to their gelation. In this study, we reported the gels formed from amorphous acemetacin (ACM) for the first time. Gelation was promoted at conditions of lower pH, higher temperature and lower ionic strength. Solid-state characterizations suggested that ACM gels may be formed by recrystallization. This mechanism provides a new direction in facilitating the elimination of gelation for amorphous drugs. Moreover, it also provides the basis for the development of sustained-release formulations using the gelation properties.

Gelation Elimination and Crystallization Inhibition by Co-Amorphous Strategy for Amorphous Curcumin

In the previous study, the development of amorphous curcumin (CUR) aimed to enhance the solubility/dissolution of CUR by disrupting its crystal lattice, but it unexpectedly showed a decreased dissolution than its crystalline counterpart on account of gel formation in its dissolution process. Whether such gelation could be eliminated by co-amorphous strategy was answered in this study. Herein, CUR by co-amorphization with chlorogenic acid (CHA) was successfully prepared using quench cooling. The formed co-amorphous material (namely CUR-CHA CM) eliminated the gelation and hence performed superior dissolution performance than crystalline/amorphous CUR. Meanwhile, it exhibited higher physical stability than amorphous CUR during dissolution as well as under long-term/accelerated conditions. To further study the such enhancement mechanism, the internal molecular interactions were investigated for CUR-CHA CM in the solid state as well as in aqueous solution. FTIR and solid-state ¹³C NMR spectra confirmed that intermolecular hydrogen bonds formed between CUR and CHA after co-amorphization. Furthermore, the nucleation of CUR was significantly inhibited by CHA in an aqueous solution, thus maintaining the supersaturated dissolution for a long time. The present study offers a feasible strategy to eliminate gelation and enhance stability of amorphous solids by co-amorphization and crystallization inhibition.

Recent advances on small molecular gels: formation mechanism and their application in pharmaceutical fields

INTRODUCTION

As an essential complement to chemically cross-linked macromolecular gels, drug delivery systems based on small molecular gels formed under the driving forces of non-covalent interactions are attracting considerable research interest due to their potential advantages of high structural functionality, lower biological toxicity, reversible stimulus-response, and so on.

AREA COVERED

The present review summarizes recent advances in small molecular gels and provides their updates as a comprehensive overview in terms of gelation mechanism, gel properties, and physicochemical characterizations. In particular, this manuscript reviews the effects of drug-based small molecular gels on the drug development and their potential applications in the pharmaceutical fields.

EXPERT OPINION

Small molecular-based gel systems, constructed by inactive compounds or active pharmaceutical ingredients, have been extensively studied as carriers for drug delivery in pharmaceutical field, such as oral formulations, injectable formulations, and transdermal formulations. However, the construction of such gel systems yet faces several challenges such as rational and efficient design of functional gelators and the great occasionality of drug-based gel formation. Thus, a deeper understanding of the gelation mechanism and its relationship with gel properties will be conducive to the construction of small molecular gels systems and their future application.

Co-amorphous Drug Delivery Systems: a Review of Physical Stability, In Vitro and In Vivo Performance

Over the past few decades, co-amorphous solids have been used as a promising approach for delivering poorly water-soluble drugs. Co-amorphous solids, comprising pharmacologically relevant drug substances or excipients, improve physical stability, solubility, dissolution, and bioavailability compared with single amorphous ingredients. In this review, we have summarized recent advances in physical stability and in vitro and in vivo performances of co-amorphous solids. We have highlighted the role of molar ratio, molecular interaction, and mobility that affects the physical stability of co-amorphous solids. This review delves deep as to how co-amorphous solids affect the physicochemical properties in vitro and in vivo. We also described the challenges to the formulation of co-amorphous solids. A better understanding of the mechanisms of the physical stability, in vitro and in vivo performance of co-amorphous solids, and proper selection of the co-former is likely to expedite the development of robust co-amorphous-based pharmaceutical formulations and can address the challenges associated with the delivery of poorly soluble drugs.

A novel soluble lornoxicam-sodium chelate monohydrate with improved plasticity and tabletability

Lornoxicam (LOR), a BCS Ⅱ nonsteroidal anti-inflammatory drug, has been clinically utilized for moderate to severe acute pain management. However, it has poor water solubility and insufficient tabletability, leading to erratic absorption and challenge in tablet processability. This study reported a novel solid state of LOR (i.e., LOR sodium chelate monohydrate, LOR-Na·H₂O) with significantly improved solubility, dissolution rate and tabletability. The prepared chelate (CCDC No.: 2125157) contains LOR^-, Na⁺, and H₂O in a molar ratio of 1:1:1, where Na⁺ ions bridged with O(5) of amide group, and N(2) of pyridine group on LOR^-, as well as O(4) on H₂O through coordination bonds. LOR-Na·H₂O displayed a superior dissolution rate (5∼465 folds) than commercial LOR due to its increased wettability (contact angle: 74.5° vs 85.6°) and lower solvation free energy (∼2-fold). In addition, the significant improvement in tabletability was caused by high plasticity and deformability, which was attributed to its special interlayer gliding with weak bonding interactions across layers but strong coordination bonding interactions within layers. The novel LOR-Na·H₂O with significantly enhanced pharmaceutical performance offers a promising strategy for further product development.

Effect of sodium lauryl sulfate-mediated gelation on the suppressed dissolution of crystalline lurasidone hydrochloride and a strategy to mitigate the gelation

In dissolution test, the surfactant sodium lauryl sulfate (SLS) is usually added to increase the dissolution of insoluble drugs and achieve the sink condition. However, the current study found that 0.1 % SLS would significantly decrease the dissolution of crystalline lurasidone hydrochloride (LH, a BCS Ⅱ drug). The aim of this study was to clarify the mechanism of this unexpected phenomenon and explore a strategy for mitigating the negative effect of SLS on the dissolution of LH. Sample characterizations (such as PLM, DSC, PXRD, IR and NMR) confirmed that the insoluble single-phase amorphous LH-SLS complex (with a single T_g at 35.2 °C) formed during dissolution in 0.1 % SLS aqueous solution via electrostatic interaction, tetrel bond interaction, and hydrophobic effect. Due to the plasticization effect of water, the transition of amorphous LH-SLS from its glassy state to viscous supercooled liquid state led to the gel formation, and suppressd the dissolution of LH. Meanwhile, the solubility curve of LH in SLS aqueous solution at various concentrations exhibited an unusual V-shaped feature, with the CMC value of SLS serving as the inflection point, since the gel degree was attenuated due to the micelle solubilization of SLS. Additionally, an innovative strategy was developed to alleviate the inhibiting effect of SLS on LH dissolution based on the potential competitive interactions. This study not only enriches the internal mechanism of surfactant-inhibited drug dissolution but also informs an effective strategy to mitigate the gelation.

Improved Pharmaceutical Properties of Honokiol via Salification with Meglumine: an Exception to Oft-quoted ∆pKa Rule

Honokiol (HK), a BCS class II drug with a wide range of pharmacological activities, has poor solubility and low oral bioavailability, severely limiting its clinical application. In the current study, incorporating a water-soluble meglumine (MEG) into the crystal lattice of HK molecule was performed to improve its physicochemical properties. The binary mixture of HK and MEG was obtained by anti-solvent method and characterized by TGA, DSC, FTIR, and PXRD. The SCXRD analysis showed that two HK^- molecules and two MEG⁺ molecules were coupled in each unit cell via the ionic interaction along with intermolecular hydrogen bonds, suggesting the formation of a salt, which was further confirmed by the XPS measurements. However, the ∆pK_a value between HK and MEG was found to be less than 1, which did not follow the oft-quoted ∆pK_a rule for salt formation. After salification with MEG, the solubility and dissolution rate of HK exhibited 3.50 and 25.33 times improvement than crystalline HK, respectively. Simultaneously, the powder flowability, tabletability and stability of HK-MEG salt was also significantly enhanced, and the salt was not more hygroscopic, and that salt formation did not compromise processability in that regard. Further, in vivo pharmacokinetic study showed that C_max and AUC_0-t of HK-MEG salt were enhanced by 2.92-fold and 2.01-fold compared to those of HK, respectively, indicating a considerable improvement in HK oral bioavailability.

Apigenin-oxymatrine binary co-amorphous mixture: Enhanced solubility, bioavailability, and anti-inflammatory effect

Apigenin (APG) is a functional ingredient in many foods, but its poor water solubility results in low bioavailability. This study aimed at delivering APG and improving bioavailability by a food-friendly co-amorphous formulation of APG with oxymatrine (OMT). After preparation of co-amorphous mixture (CM), characterized by powder x-ray diffraction and thermal analysis. Then, the presence of hydrogen bonds was confirmed by vibrational spectroscopy and molecular dynamics simulation. Furthermore, phase solubility and solubility studies, as well as dissolution test indicated that complexation occurred between APG and OMT in solution, which significantly improved the solubility and dissolution of APG-OMT CM. Additionally, pharmacokinetics and biological activity indicated that APG-OMT CM exhibited higher oral bioavailability and anti-inflammatory effect than pure APG. These results suggest that APG-OMT CM may be great potential for application in functional food. Importantly, the study provides a promising delivery system to improve the bioavailability of hydrophobic food ingredients.

Recent Advances in Enhancement of Dissolution and Supersaturation of Poorly Water-Soluble Drug in Amorphous Pharmaceutical Solids: A Review

Amorphization is one of the most effective pharmaceutical approaches to enhance the dissolution and oral bioavailability of poorly water-soluble drugs. In recent years, amorphous formulations have been experiencing rapid development both in theoretical and practical application. Based on using different types of stabilizing agents, amorphous formulations can be mainly classified as polymer-based amorphous solid dispersion, coamorphous formulation, mesoporous silica-based amorphous formulation, etc. This paper summarizes recent advances in the dissolution and supersaturation of these amorphous formulations. Moreover, we also highlight the roles of stabilizing agents such as polymers, low molecular weight co-formers, and mesoporous silica. Maintaining supersaturation in solution is a key factor for the enhancement of dissolution profile and oral bioavailability, and thus, the strategies and challenges for maintaining supersaturation are also discussed. With an in-depth understanding of the inherent mechanisms of dissolution behaviors, the design of amorphous pharmaceutical formulations will become more scientific and reasonable, leading to vigorous development of commercial amorphous drug products.

[Construction of Coamorphous Technology Aimed at Improving Membrane Permeability and Application to Emulsion]

The coamorphous formation between naringenin (NRG) and hesperetin (HPT) was investigated with the aim of enhancing their solubility and membrane permeability. In addition, application to emulsion of coamorphous was investigated. The melt-quenched particles (MQPs) of NRG and HPT were prepared in a range of molar ratios of NRG/HPT (3/1 to 1/3). All MQPs showed the amorphous state and single glass transition temperature. MQPs of NRG/HPT (1/1) could kept the amorphous state under storage. On the other hand, other MQPs recrystallized from the compound with a higher molar ratio. These results indicated that NRG and HPT formed the coamorphous at a molar ratio of 1 to 1. The coamorphous formation enhanced the apparent solubilities of NRG and HPT in aqueous media. Furthermore, MQPs of NRG/HPT (1/1) increased a permeated amount of NRG and HPT via the synthetic membrane in Franz Cell. When the solubility of NRG and HPT in oil components were investigated, the MQPs of NRG/HPT (1/1) enhanced the solubility of both compounds. This study highlighted the importance of coamorphous formation as a formulation to enhance solubility in oil components and aqueous media, and membrane permeability of both NRG and HPT.

Applications of innovative technologies to the delivery of antipsychotics

Psychosis is a high-incidence pathology associated with a profound alteration in the perception of reality. The limitations of drugs available on the market have stimulated the search for alternative solutions to achieve effective antipsychotic therapies. In this review, we evaluate innovative formulations of antipsychotic drugs developed through the application of modern pharmaceutical technologies, including classes of micro and nanocarriers, such as lipid formulations, polymeric nanoparticles (NPs), solid dispersions, and cyclodextrins (CDs). We also consider alternative routes of administration to the oral and parenteral ones currently used. Improved solubility, stability of preparations, and pharmacokinetic (PK) and pharmacodynamic (PD) parameters confirm the potential of these new formulations in the treatment of psychotic disorders.

Charge-assisted bond and molecular self-assembly drive the gelation of lenvatinib mesylate

Lenvatinib mesylate (LM) is a first-line anticancer agent for the treatment of unresectable hepatocellular carcinoma, while it formed viscoelastic hydrogel when contacting with aqueous medium, which would significantly hinder its in vitro dissolution. The aim of this study was to systematicly explore the gelation mechanism and gel properties via thermal analysis, rheology, morphology and spectroscopy studies. The formed hydrogel was found to be composed of a new polymorph of crystalline LM, and its mechanical strength depended on the cross-linking degree of the fibrillar network structure. Spectroscopy analyses revealed that the intermolecular hydrogen bonds (the bifurcated hydrogen bond between the adjacent urea groups and the NH⋯OC hydrogen bond between the primary amide groups) as well as π-π stacking interactions (between the benzene ring and the quinoline ring) were suggested to be the driving forces for the self-assembly of LM during gelation process. Additionally, no gelation phenomenon was observed when suspending the base form lenvatinib in water, while it could form gel in various acidic solutions (e.g. hydrochloric acid, phosphoric acid and methanesulfonic acid) because the regenerated N⁺-H group increased the solubility of lenvatinib and promoted the balance between the dissolution or aggregation of LX (X: acid radical ion) molecules in solutions. In conclusion, the charge-assisted bond N⁺-H in LM molecule and intermolecular non-covalent interactions drived the hydrogel formation of LM in aqueous media. This study elucidates the gelation mechanism and gel properties of LM hydrogel, which would be helpful to figure out strategy to eliminate its gelation fundamentally and pave the way for its further formulation development in future.

Puerarin-Na Chelate Hydrate Simultaneously Improves Dissolution and Mechanical Behavior

Puerarin monohydrate (PUEM), as the commercial solid form of the natural anti-hypertension drug puerarin (PUE), has low solubility, poor flowability, and mechanical properties. In this study, a novel solid form as PUE-Na chelate hydrate was prepared by a reactive crystallization method. Crystal structure analysis demonstrated that PUE-Na contains PUE^-, Na⁺, and water in a molar ratio of 1:1:7. It crystallizes in the monoclinic space group P2₁, and Na⁺ is linked with PUE^- and four water molecules through Na⁺ ← O coordination bonds. Another three crystal water molecules occupy channels along the crystallographic b-axis. Observing along the b-axis, the crystal structure features a distinct tubular helix and a DNA-like twisted helix. The complexation between Na⁺ and PUE^- in aqueous solution was confirmed by the Na⁺ selective electrode, indicating that PUE-Na chelate hydrate belongs to a type of chelate rather than organic metal salt. Compared with PUEM, PUE-Na exhibited a superior dissolution rate (i.e., ∼38-fold increase in water) owing to its lower solvation free energy and clear-enriched exposed polar groups. Moreover, PUE-Na enhanced the tabletability and flowability of PUEM, attributing to its better elastoplastic deformation and lower-friction crystal habit. The unique PUE-Na chelate hydrate with significantly enhanced pharmaceutical properties is a very promising candidate for future product development of PUE.

Sinomenine-phenolic acid coamorphous drug systems: Solubilization, sustained release, and improved physical stability

Sinomenine (SIN), isolated from Caulis sinomenii, is a benzyltetrahydroisoquinoline-type alkaloid with potent anti-inflammatory and analgesic effects. SIN-HCl has been used in the forms of tablets or enteric-coated tablets in the treatment of rheumatoid arthritis in China for years, while its short half-life leads to attenuated therapeutic effects and serious side effects. In the current study, three phenolic acids, including salicylic acid (SAA), 2,3-dihydroxybenzoic acid (23DHB), and 2,4-dihydroxybenzoic acid (24DHB), were firstly employed as coamorphous coformers to prepare three binary SIN-phenolic acid coamorphous systems. These new coamorphous systems were characterized by powder X-ray diffraction (PXRD), modulated temperature differential scanning calorimetry (mDSC), and Fourier transform infrared spectroscopy (FTIR). The formation of SIN-phenolic acid coamorphous systems are supported by the absence of diffraction peaks in their PXRD spectra, as well as the single T_gs of three samples (i.e., SIN-SAA, SIN-23DHB, and SIN-24DHB) at 109.5 °C, 124.9 °C, and 135.3 °C. Importantly, the salt formation between SIN and phenolic acids was observed in FTIR. In three coamorphous systems, coamorphous SIN-24DHB shows superior physicochemical stability under both low humidity and accelerated storage conditions. They were also more soluble than crystalline SIN, while were released slower than the commercial SIN-HCl in dissolution experiments. Therefore, our study suggests that phenolic acids may be used as a new type of coformers in the preparation of coamorphous systems for active pharmaceutical ingredients.

Coamorphous System of Florfenicol-Oxymatrine for Improving the Solubility and Dissolution Rate of Florfenicol: Preparation, Characterization and Molecular Dynamics Simulation

Coamorphous system has proved to be an effective approach to improve the solubility of BCSⅡ drugs. Florfenicol (FF) is a widely used veterinary antibiotic but has poor aqueous solubility. Therefore, the coamorphous system of florfenicol and oxymatrine (OMT) formulated at 1:1 and 1:2 M ratios were prepared by using solvent evaporation, followed by a series of characterization in terms of PXRD, DSC, FTIR and Raman spectroscopy. It was found that FF and OMT are miscible according to Hansen solubility parameters. The molecular electrostatic potential (MEP) and radial distribution function (RDF) analysis demonstrated the possible hydrogen bond interaction in coamorphous system, which was confirmed by FTIR and Raman spectra. The coamorphous FF-OMT (1:1) maintained stability for 60 days at 25 °C/0% RH and 30 days at 40 °C/75% RH, which may be attributed to better molecular miscibility of FF and OMT and the strong hydrogen bond of O-H (FF)⋯O-N (OMT) and N-H (FF)⋯O-N (OMT). In addition, the apparent solubility and permeability, dissolution and intrinsic dissolution rate (IDR) of the acquired coamorphous solids were obviously increased compared with crystalline FF. In conclusion, a drug-drug coamorphous formulation can be applied to improve the solubility and dissolution of crystalline FF.

Influence of the pK a Value of Cinnamic Acid and P-Hydroxycinnamic Acid on the Solubility of a Lurasidone Hydrochloride-Based Coamorphous System

Coamorphization of a poorly water-soluble active pharmaceutical ingredient (API) has been proven to be effective in improving its solubility. Generally, API can form multiple coamorphous systems with different coformers. However, it remains unclear how the pK _a value of different coformers influences the solubility of the API. In this study, structurally related cinnamic acid (CA, pK _a = 4.37) and p-hydroxycinnamic acid (pHCA, pK _a = 4.65) were chosen as coformers for the coamorphization of lurasidone hydrochloride (LH). To investigate the influence of the pK _a value of the coformers on the solubility of LH, LH-CA/pHCA coamorphous systems were prepared by the vacuum rotary evaporation method and characterized by powder X-ray diffraction and differential scanning calorimetry. Fourier-transform infrared spectroscopy, Raman spectroscopy, and molecular dynamics (MD) simulations were employed to investigate the intermolecular interaction of the coamorphous systems. It was found that the solubility of LH in the coamorphous LH-pHAC with a higher-pK _a coformer was higher than that of the coamorphous LH-CA. In addition, according to the solubility product principle-based formula derivation, we established the functional relationship between the solubility of LH and the pK _a of the coformers at different-pH buffering solution. It was found that the coformer with a larger pK _a value would be more beneficial to improve the solubility profile of LH. Collectively, the current study offers an effective strategy to improve the poor solubility of drugs by increasing the pK _a value of the coformer in coamorphous systems.

A novel lurasidone hydrochloride–shikimic acid co-amorphous system formed by hydrogen-bonding interaction with the retained pH-dependent solubility behavior

The current study was aimed at investigating the lurasidone hydrochloride–shikimic acid co-amorphous system using a new type of organic acid.