Crystal engineering of active pharmaceutical ingredients to improve solubility and dissolution rates

Pharmacokinetics of nano- and microcrystal formulations of low solubility compounds after intramuscular injection to mice

OBJECTIVES

The aim of this study was to investigate the pharmacokinetics (PK) of poorly soluble compounds when administered intramuscularly (i.m.) as crystalline particles of different sizes.

METHODS

Three uncharged compounds (griseofulvin, AZ'72, and AZ'07) with varying aqueous solubility were dosed to mice at 10 and 50 mg/kg as nano- and microparticle formulations. The PK of the compounds was evaluated.

KEY FINDINGS

The smaller particles of the drugs resulted in higher maximum plasma concentration (Cmax) and area under the plasma concentration-time profile (AUC) at 50 mg/kg. There was a dose-proportional increase in AUC but less than dose dose-proportional increase in Cmax. The evaluation at 10 mg/kg was more complex as increased exposure for nanoparticles was only observed for griseofulvin which has the highest solubility. In addition, there was an increase in half-life with an increase in dose.

CONCLUSIONS

This study highlights that general expectations based on in vitro dissolution (i.e. that smaller particles dissolve faster than larger particles when surrounded by liquid) do not always translate to in vivo and demonstrates the importance of understanding the physicochemical properties of the drug, the characteristics of the formulations and the microphysiology at the delivery site.

Case study: cremophor EL-based liquid formulations as simple substitutes for amorphous solid dispersions in early preclinical in vivo studies

OBJECTIVES

The objective of the present case study was to increase the exposure of the poorly soluble crystalline compound A.

METHODS

Mice received 10 mg/kg of crystalline compound A formulated in eight different cosolvent, oil, and cyclodextrin mixtures.

KEY FINDINGS

In all cases, AUC0-24h and maximum blood/plasma concentration (Cmax) were in the range of 6-16 µM × h and <1.4 µm, respectively, with a bioavailability below 18%. When 6% cremophor (CrEL) was added to three selected vehicles, AUC0-24h and Cmax increased ~5-10 times. The obtained pharmacokinetic profile of the most improved formulation using CrEL was possible to superimpose on the one obtained after administration of a CrEL-free amorphous solid dispersion (ASD, HPMC-AS:drug, 80:20) suspension of compound A.

CONCLUSIONS

It is crucial to find an optimal screen vehicle as early as possible for a poorly water-soluble lead series and then avoid time and resource-consuming vehicle testing of multiple compounds in vivo. An ASD approach is more suited for clinical development when more time and resources are allocated to the project. In this case study, some preclinical formulations were used to maximize exposure but also as preindicators for ASDs later in the development chain.

The origin of synthons and supramolecular motifs: beyond atoms and functional groups

A four-membered R22(4) supramolecular motif formed by S...S and S...I chalcogen-bonding interactions in the crystal structure of 4-iodo-1,3-dithiol-2-one (C3HIOS2, IDT) is analysed and compared with a similar R22(4) motif (stabilized by Se...Se and Se...O chalcogen bonds) observed in the previously reported crystal structure of selenaphthalic anhydride (C8H4O2Se, SePA) through detailed charge density analysis. Our investigation reveals that the chalcogen-bonding interactions participating in the R22(4) motifs observed in the two structures have the same characteristic orientation of local electrostatic electrophilic...nucleophilic interactions while involving different types of atoms. We carried out Cambridge Structural Database searches for synthons and supramolecular motifs involving chalcogen-, halogen- and hydrogen-bonding (ChB, XB and HB) interactions. Geometrical characterizations and topological analyses of the electron density ρ(r) and its negative Laplacian function [L(r) = -∇2ρ(r)] indicate that all the bonding interactions forming the motifs are driven by local electrophilic...nucleophilic interactions between complementary charge concentration (CC) and charge depletion (CD) sites present in the valence shells of the atoms, regardless of the atoms and functional groups involved. The graph-set assignment Gda(n) (G = C, R, D or S), formerly developed by Etter [Acc. Chem. Res. (1990), 23, 120-126] for HB interactions, is a convenient way to describe the connectivity in supramolecular motifs based on electrophilic...nucleophilic interactions (such as ChB, XB and HB interactions), exchanging the number of atomic acceptors (a) and donors (d) with the number of nucleophilic (n: CC) and electrophilic (e: CD) sites, and the number of atoms building the motif n by m, leading to the new graph-set assignment Gen(m) (G = C, R, D or S). Geometrical preferences in the molecular assembly of synthons and other supramolecular motifs are governed by the relative positions of CC and CD sites through CC...CD interactions that, in most cases, align with the internuclear directions within a <15° range despite low interaction energies. Accordingly, beyond atoms and functional groups, the origin of recurrent supramolecular structures embedded within different molecular environments is found in the local electrostatic complementarity of electrophilic and nucleophilic regions that are placed at particular geometries, driving the formation and the geometry of synthons and supramolecular motifs by directional and locally stabilizing electrostatic interactions.

Surface Defects and Crystal Growth of Apremilast Benzoic Acid Cocrystals

A cocrystallization process of the active pharmaceutical ingredient apremilast with benzoic acid is explored in this work. The aim of the study is to adjust operating conditions during the crystallization to purposefully tune the dissolution properties of the final product. Understanding the cocrystallization is key to obtaining a consistent, high-quality product, as well as tuning other properties such as powder flowability or dissolution properties. It was discovered early in development that the studied cocrystallization process does not follow the common rules of crystallization. Better crystals were obtained at faster cooling rates and worse crystals at slower cooling rates. Interestingly, this can be explained by crystal collisions and a two-phase growth of the crystals. Standard operating conditions were further tested, resulting in different shapes and sizes of the product. Different types of produced crystals were tested in a dissolution apparatus and provided significantly modified dissolution profiles.

How Temperature Change Affects the Lattice Parameters, Molecular Conformation, and Reaction Cavity in Enantiomeric and Racemic Crystals of Thalidomide

For the single crystals of thalidomide (C13H10N2O4, TD) grown by the solvent evaporation method, the temperature dependences of the crystal structures have been investigated over a wide temperature range between 100 and 423.15 K. Comparing the α-form of a racemic TD crystal, which consists of symmetric heterochiral dimers and belongs to P21/n space group, with the enantiomeric TD crystal, which belongs to P21 and consists of asymmetric (pseudosymmetric) homochiral dimers, there have been clear differences in the temperature-dependent changes of the lattice parameters, the isobaric linear thermal expansion coefficients (along the crystallographic and the principal Cartesian axes), the volumetric expansion coefficients of the unit cell, and the structures of hydrogen-bonded dimer in the crystal such as intra- and intermolecular dihedral angles, cavities (reaction cavities), and the hydrogen-bond length. In the asymmetric homochiral dimers, one monomer with a larger reaction cavity changes its intramolecular dihedral angle with temperature, while the other monomer with a smaller cavity does not. In contrast, in the symmetric heterochiral dimers, two monomers with the same cavity volume similarly change their intramolecular dihedral angles with the temperature. Such differences in the temperature-dependent conformational changes between asymmetric and symmetric dimers cause differences between enantiomeric and racemic crystals.

Pure drug nanomedicines - where we are?

Pure drug nanomedicines (PDNs) encompass active pharmaceutical ingredients (APIs), including macromolecules, biological compounds, and functional components. They overcome research barriers and conversion thresholds associated with nanocarriers, offering advantages such as high drug loading capacity, synergistic treatment effects, and environmentally friendly production methods. This review provides a comprehensive overview of the latest advancements in PDNs, focusing on their essential components, design theories, and manufacturing techniques. The physicochemical properties and in vivo behaviors of PDNs are thoroughly analyzed to gain an in-depth understanding of their systematic characteristics. The review introduces currently approved PDN products and further explores the opportunities and challenges in expanding their depth and breadth of application. Drug nanocrystals, drug-drug cocrystals (DDCs), antibody-drug conjugates (ADCs), and nanobodies represent the successful commercialization and widespread utilization of PDNs across various disease domains. Self-assembled pure drug nanoparticles (SAPDNPs), a next-generation product, still require extensive translational research. Challenges persist in transitioning from laboratory-scale production to mass manufacturing and overcoming the conversion threshold from laboratory findings to clinical applications.

Impact of agglomeration on in vitro performance of long-acting injectable suspensions

Long-acting injectable (LAI) suspensions are controlled drug delivery systems that provide sustained drug release over durations ranging from one to six months. Although it is recognized that the particle agglomeration behavior could play a critical role on product clinical performance, factors that can affect this behavior have not yet been fully understood. This study explores the impact of particle size modification techniques, shear force, and agglomeration state on the in vitro drug release of LAI suspensions. Depo-Provera 150® [medroxyprogesterone acetate (MPA)] was used as the model drug product. Five qualitative (Q1) and quantitative (Q2) equivalent MPA suspensions (FA, FB, FC, FD, FE) were prepared with formulation and processing differences. Physicochemical characterization, including particle size, morphology, sedimentation value, and viscosity, was conducted. The effects of shear force, induced by shaking, syringe usage, ultrasonication, and stirring, on the agglomeration behavior of the MPA suspensions were also investigated. In vitro dissolution studies were performed using a novel in-house adapter. Characterization revealed that particles in MPA suspensions exist as weak agglomerates, strong agglomerates, or primary particles. Formulations FA and FC, containing weak agglomerates, were sensitive to shear and showed slight variations in drug release rates. Formulation FB, containing strong agglomerates, resisted low to medium shear and exhibited faster-than-expected drug release due to de-agglomeration in surfactant-containing media. Formulations FD and FE, composed of primary particles, tended to agglomerate during dissolution, resulting in slower release rates. This research highlights the critical role of particle agglomeration and agglomeration behavior in understanding drug release from MPA suspension and other similar LAI suspensions. The findings emphasize the need for thorough characterization of particle states and their response to shear force to optimize LAI formulations for consistent and predictable in vitro drug release.

Open micro-combinatorial analysis systems of crystal growth critical points of a π-conjugated molecule in ionic liquid nanoliter droplets

Crystal engineering methodologies based on reproducible and high-throughput fabrication of high-quality single crystals have attracted much attention. Crystal formation and growth are governed by crystal growth theory. The driving force of crystallization is systematically represented with phase diagrams. However, constructing phase diagrams usually requires relatively large quantities of samples (milligrams to grams) and substantial time (weeks to months) to evaluate many conditions. Therefore, an easy and quick methodology to obtain phase diagrams, revealing critical conditions for valuable samples, is required. Here, we proposed a new method to obtain phase diagrams based on nanoliter droplet arrays of nonvolatile ionic liquids prepared by inkjet printing. Anthracene derivatives and 1-octyl-4-methylpyridinium derivatives were used as the solute and solvent, respectively. Optimization of ejection conditions, such as applied voltage, frequency, pulse width, and head temperature, enabled the formation of a 0.5 nL droplet per ejection. Inkjet printing under these conditions formed nanodroplet arrays on substrates at a droplet-patterned density of ca. 50 dots per cm2. The volume of each patterned droplet was varied from 10 to 100 nL by changing the number of ejections. The dissolution temperature of anthracene at each concentration was obtained at a heating rate of 0.2 °C min-1. This heating rate was found to be 10 times faster than the conventional technique. The same phase diagram as that prepared by the conventional technique was obtained in the range of 75-300 mM. The standard deviation of the dissolution temperatures was 0.8 °C (2.5%). This technique will facilitate the crystallization of multiple and valuable samples.

Applications and prospects of biomaterials in diabetes management

Diabetes is a widespread metabolic disorder that presents considerable challenges in its management. Recent advancements in biomaterial research have shed light on innovative approaches for the treatment of diabetes. This review examines the role of biomaterials in diabetes diagnosis and treatment, as well as their application in managing diabetic wounds. By evaluating recent research developments alongside future obstacles, the review highlights the promising potential of biomaterials in diabetes care, underscoring their importance in enhancing patient outcomes and refining treatment methodologies.

Effect of pH and Buffer Capacity of Physiological Bicarbonate Buffer on Precipitation of Drugs

The purpose of this study was to investigate the effect of the pH and buffer capacity (β) of physiological bicarbonate buffer solutions (BCB) on drug precipitation. The precipitation profiles of poorly soluble drugs in BCB were evaluated by using a pH-shift precipitation test. Phosphate buffer solutions (PPB) were used for comparison. Two weakly acidic drugs (pKa: 4.9 and 7.0) and two weakly basic drugs (pKa: 6.1 and 8.3) were used as model drugs. The bulk phase pH value (pHbulk) and β values were set to cover the physiological range in the small intestines (pH: 5.5 to 7.5, β: 2.2 to 17.6 mM/ΔpH). A floating lid was used to maintain the pHbulk of BCB to avoid CO2 loss. It was also applied to PPB to align the experimental conditions. Each drug was completely dissolved in HCl (pH 3.0, for weakly basic drugs) or NaOH (pH 11.0, for weakly acidic drugs) solutions (450 mL, 50 rpm, 37 °C). The pHbulk value was then shifted to the neutral pH region by adding a 10-fold concentrated buffer solution (50 mL, final volume of 500 mL). The initial total drug concentration (neutral + ionized species) was set so that the concentration and supersaturation ratio of the neutral species were the same under all pHbulk conditions. The solid forms of the precipitates were determined by powder X-ray diffraction and differential scanning calorimetry. In BCB, as pHbulk was increased above (for weakly acidic drugs) or decreased below (for weakly basic drugs) the drug pKa value, the precipitation of the free form solid became slower. As β was increased, drug precipitation in BCB became faster. Drug precipitation in PPB was faster than that in BCB and less affected by pHbulk and β. In BCB, at pHbulk at which a drug is ionizable, the surface pH of the precipitating particles can differ from pHbulk because of the slow hydration process of CO2. In conclusion, pHbulk and β affected the precipitation of weakly acidic and basic drugs in BCB. As BCB is a physiological buffer in the small intestine, it should be used for precipitation studies of weakly acidic and basic drugs.

From Unwanted Annoyances to Oral Delivery Saviors: The Rollercoaster Journey of Amorphous Drugs

The benefits and disadvantages of amorphous drugs have been topics of discussion for nearly a century. In the post-World War II era when drug discovery burgeoned, amorphous drugs were largely regarded as unfavorable forms for commercial products. This sentiment began to change as the number of poorly water-soluble drugs, which targeted a broader range of disease states and emerged from high throughput screening assays, began to increase. The solubility advantage of amorphous drugs was long recognized at this juncture, but unease persisted over potential conversions back to the less soluble crystal form during product storage. Successful development of early amorphous products based on amorphous solid dispersion formulations, where a suitable polymer is molecularly mixed with the drug resulting in inhibition of drug crystallization, gradually mitigated concerns. This historical perspective of amorphous drugs provides an overview of timelines and key milestones and culminates by considering remaining challenges and the future outlook.

Accelerating structure prediction of molecular crystals using actively trained moment tensor potential

Inspired by the recent success of machine-learned interatomic potentials for crystal structure prediction of inorganic crystals, we present a methodology that exploits moment tensor potentials (MTP) and active learning (based on maxvol algorithm) to accelerate structure prediction of molecular crystals. Benzene and glycine are used as test systems. The obtained potentials are able to rank different benzene and glycine polymorphs in good agreement with density-functional theory. Hence, we argue that MTP can be used to accelerate the computationally guided polymorph search.

Solvatomorphic diversity dictates the stability and solubility of metal-organic polyhedra

The reaction between molybdenum(ii) acetate and 5-aminoisophthalic acid (H2Iso-NH2) afforded [Mo12O12(μ2-O)12(Iso-NH2)12]12-, a novel molybdenum(v) metal-organic polyhedron (MOP) with a triangular antiprismatic shape stabilized by intramolecular N-H⋯O hydrogen bonds. The synthesis conditions, particularly the choice of solvent and reaction time, led to the precipitation of the Mo(v)-MOP in five distinct crystalline forms. These forms vary in their packing arrangements, co-crystallized solvent molecules, and counter-cations, with three phases containing dimethylammonium (dma+) and the other two containing diethylammonium (dea+). Each solvatomorph exhibits unique physical properties, including differences in porosity, and stability. These properties were discerned through empirical observations and supported by density functional theory calculations. Remarkably, the solubility of these MOP solvatomorphs in water was determined for the first time, with values of 4.30(2) g L-1 for a (dma)12[Mo(v)-MOP] phase, and 10.25(7) g L-1 and 14.41(10) g L-1 for two (dea)12[Mo(v)-MOP] phases. Additionally, aqueous solutions of the Mo(v)-MOP were found to conduct electricity as weak electrolytes, showcasing their potential for applications in fields requiring partially ionized species.

Study of chemical reactivity and molecular interactions of the hydrochlorothiazide-4-aminobenzoic acid cocrystal using spectroscopic and quantum chemical approaches

In this study, the molecular, electronic, and chemical properties of the drug hydrochlorothiazide (HCTZ) are determined after cocrystallization with 4-aminobenzoic acid (4-ABA). Analysis has been performed to understand how those variations lead to alteration of physical properties and chemical reactivity in the cocrystal HCTZ-4ABA. IR and Raman characterizations were performed along with quantum chemical calculations. A theoretical investigation of hydrogen bonding interactions in HCTZ-4ABA has been conducted using two functionals: B3LYP and wB97X-D. The results obtained by B3LYP and wB97X-D are compared which leads to the conclusion that B3LYP is the best applied function (density functional theory) to obtain suitable results for spectroscopy. The chemical reactivity descriptors are used to understand various aspects of pharmaceutical properties. Natural bond orbital (NBO) analysis and quantum theory of atoms (QTAIM) are used to analyze nature and strength of hydrogen bonding in HCTZ-4ABA. QTAIM analyzed moderate role of hydrogen bonding interactions in HCTZ-4ABA. The calculated HOMO-LUMO energy gap shows that HCTZ-4ABA is chemically more active than HCTZ drug. These chemical parameters suggest that HCTZ-4ABA is chemically more reactive and softer than HCTZ. The results of this study suggest that cocrystals can be a good alternative for enhancing physicochemical properties of a drug without altering its therapeutic properties.

In-Situ Monitoring of Dissolution and Crystallization Processes of Carbamazepine Using Low-Frequency Raman Spectroscopy and Multivariate Analysis

Optimization of the manufacturing process based on scientific evidence is essential for quality control of active pharmaceutical ingredients. Real-time monitoring can ensure the production of stable quality crystals in the crystallization process. Raman spectroscopy is an attractive tool for pharmaceutical quality evaluation and process analytical technology because of its ability to analyze samples non-destructively and rapidly. In this study, we attempted to monitor the crystal polymorphs of carbamazepine (CBZ I and CBZ III) during the dissolution and crystallization processes using low-frequency Raman spectroscopy, which can reflect differences in lattice vibrations originating from polymorphs in the scattering peaks. Furthermore, using multivariate analysis of the obtained spectra, we attempted to develop a model that enables the quantification of each polymorph. A partial least squares was performed to build the prediction model. The prediction model was built using a set of 33 calibration samples, and an external set of 12 validation samples was used to evaluate the model. The model presents a good prediction capacity. The quantitative results for the solid amount of carbamazepine in suspension calculated using the model during the dissolution and crystallization process showed results that correlated very well with the particle view results. It is suggested that low-frequency Raman spectroscopy can be used as a useful process analytical technology tool.

Interaction between newly synthesized surface-active ionic liquids with pharmaceutically active anion and bovine serum albumin

This work describes the synthesis and properties of new surface active (octyl-, and dodecyl-) imidazolium and choline-based ionic liquids with pharmaceutically active 5-fluorouracil anion (SAAPI-IL). The effect of the novel SAAPI-IL on the secondary and tertiary structure of bovine serum albumin (BSA) was studied using circular dichroism (CD) spectroscopy. The binding constants of BSA with SAAPI-IL were estimated from the fluorescence quenching of BSA. The influence of the length of the alkyl chain SAAPI-IL on the binding constant with BSA was analyzed. The localization of ions on BSA was estimated using the molecular docking method. Also, the effect of alkyl substituent length on the aggregation tendency of SAAPI-IL was studied by dynamic light scattering (DLS). Cytotoxicity and selectivity of SAAPI-ILs on cancer and normal cell lines were compared to molecular 5-fluorouracil and API-IL without the alkyl substituents. Surprisingly, increasing the length of the alkyl substituent did not increase the binding of SAAPI-IL to BSA. On the other hand, [C8Ch][FU] showed selectivity against A 549 cell line, which 5-fluorouracil does not possess.

Recent Patents on Solid Dispersions Emphasize Promising Benefits in Solubility Enhancement of Poorly Water-soluble Drugs

BACKGROUND

In the development of drug delivery systems, drugs' solubility remains the most challenging constraint. Many newly synthesized chemical compounds are available, but they involve low solubility and poor permeability restrictions. Among various drug delivery systems, the utilization of solid dispersion technologies has become more focused due to their promising benefits.

OBJECTIVE

This technology has attracted extensive attention for dissolution rate improvement along with substantial bioavailability enhancement of poorly water-soluble drug candidates.

METHODS

Many approaches have been employed for preparing solid dispersions, such as the melting method, hot melt extrusion, solvent evaporation process, fusion and kneading method, spray drying technique, co-grinding and freeze drying, supercritical fluid technology, etc. Results: A wide variety of hydrophilic and hydrophobic materials are available as carriers, which are employed in the formulation of solid dispersions. Depending on the carrier characteristics, immediate- release solid dispersions and/or controlled-release solid dispersions can be formulated. Multiple hydrophilic materials have been explored for heightening dissolution features with enhanced bioavailability of poorly water-soluble drug molecules. The availability of commercially available products further validates the utility of solid dispersion technology in drug delivery systems.

CONCLUSION

In the current manuscript, an attempt has been made to highlight the comprehensive development techniques, characterization techniques, recent solid dispersion technologies, clinical trial studies, and patented technology, along with studies heightening the dissolution behavior of numerous poorly aqueous soluble drugs. The major stability issues affecting the suitability of solid dispersions are also discussed.

The interplay between hydrogen bonds and stacking/T-type interactions in molecular cocrystals

Supramolecular synthon and hydrogen bond pairing approaches have influenced the understanding of cocrystal formation for decades, but are hydrogen bonds really the dominant interaction in cocrystals? To investigate this, an extensive analysis of 1:1 two-component cocrystals in the Cambridge Structural Database was undertaken, revealing that stacking and T-type interactions are just as, if not more important than hydrogen bonds in molecular cocrystals. A total of 84% of the most common coformers in the dataset are aromatic. When analysing cocrystal dimers, only 20% consist of solely strong hydrogen bonds, with over 50% of contacts involving stacking and T-type interactions. Combining interaction strength and frequency, both hydrogen bond and stacking/T-type interactions contribute equally to the stabilisation of cocrystal lattices. Therefore, we state that crystal engineering and cocrystal design concepts of the future should not solely revolve around supramolecular synthon pairing via hydrogen bonds, but instead consider optimising both hydrogen bonding and stacking/T-type interactions.

Encapsulation of a drug into electrospun fibers spun from water soluble polymers to control solubility and release

Electrospun fibers prepared from water-soluble polymers (PVP, PVA, and HPMC) were loaded with pregabalin, a BCS I drug, to address its fast release and adverse effects. The drug dissolved partially (1.8-2.8 wt%) in the polymers, with excess pregabalin in crystalline form within the fibers. The solubility of the drug varied with the pH of the dissolution medium. Most of the drug encapsulated into the fibers during electrospinning, but some was lost due to technical reasons. PVP showed no impact on drug release, offering no benefit as a carrier. However, PVA-based fibers exhibited considerably slower release than the dissolution rate of the neat drug and also the release rate from fibers prepared from the other polymers. This indicates the potential of PVA for using it with pregabalin in practical drug formulations with improved release properties. The pH of the dissolution medium influenced solubility and release rate for specific polymers. Overall, the study highlights the importance of polymer selection and pH control in optimizing the release profile of pregabalin in enhanced drug delivery.

A Perspective on the Permeability of Cocrystals/Organic Salts of Oral Drugs

According to the BCS classification system, the differentiation of drugs is based on two essential parameters of solubility and permeability, meaning the latter is as pivotal as the former in creating marketable pharmaceutical products. Nevertheless, the indispensable role of permeability in pharmaceutical cocrystal profiles has not been sufficiently cherished, which can be most probably attributed to two principal reasons. First, responsibility may be on more user-friendly in vitro measurement procedures for solubility compared to permeability, implying the permeability measurement process seems unexpectedly difficult for researchers, whereas they have a complete understanding of solubility concepts and experiments. Besides, it may be ascribed to the undeniable attraction of introducing new crystal-based structures which mostly leaves the importance of improving the function of existing multicomponents behind. Bringing in new crystalline entities, to rephrase it, researchers have a fairly better chance of achieving high-class publications. Although the Food and Drug Administration (FDA) has provided a golden opportunity for pharmaceutical cocrystals to straightforwardly enter the market by simply considering them as derivatives of the existing active pharmaceutical ingredients, inattention to assessing and scaling up permeability which is intimately linked with solubility has resulted in limited numbers of them in the global pharmaceutical market. Casting a glance at the future, it is apprehended that further development in the field of permeability of pharmaceutical cocrystals and organic salts requires a meticulous perception of achievements to date and potentials to come. Thence, this perspective scrutinizes the pathway of permeation assessment making researchers confront their fear upfront through mapping the simplest way of permeability measurement for multicomponents of oral drugs.

Current Perspectives on Development and Applications of Cocrystals in the Pharmaceutical and Medical Domain

In recent years, the design of pharmaceutical cocrystals has garnered significant attention. The process of cocrystallization offers a remarkable opportunity to develop drug products with enhanced properties such as improved stability, solubility, hygroscopicity, dissolution rate, and bioavailability. This detailed review delves into this evolving area, thereby exploring its relevance in pharmaceutical formulation by defining cocrystals and their practical applications and also by discussing methods for their preparation as well as characterization. It also contrasts traditional and innovative techniques for cocrystal formation. Historically, cocrystals have been synthesized using methods like solvent evaporation, grinding, and slurry techniques; however, each has its own set of limitations under specific conditions. The latest trends in cocrystal formation lean toward more advanced approaches such as spray-drying, hot melt extrusion, and supercritical fluid technology, as well as the cutting-edge technique of laser irradiation. The aim behind developing new methods is not just to address the limitations of traditional cocrystallization techniques but also to streamline the process by introducing simpler steps and enabling a continuous production workflow for cocrystal products. In general, this full-length review article offers a report on various techniques available for the creation of pharmaceutical cocrystals, along with the methods for their evaluation. Moreover, it includes reporting developments and diverse applications of cocrystals along with the commercially available cocrystals in the pharmaceutical as well as medical domains.

Pharmaceutical Properties of the Phloretin-4,4'-Bipyridine Cocrystal: Structure Analysis, Drug Release Profile, and Antioxidant Activity Research

To improve the water solubility of phloretin, we synthesized the Phl-4B cocrystal using the solvent evaporation method. Various analytical techniques including powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), 1HNMR, and single-crystal X-ray diffraction (SCXRD) were employed to evaluate the crystal thermodynamics and structure. The results of PXRD and SCXRD showed that it was a new cocrystal crystallized in the P-1 space group of the triclinic system. Thermal analysis confirmed the purity of the Phl-4B cocrystal. The equilibrium solubility of the Phl-4B cocrystal in pH 1.2 was improved. In vitro simulated digestion experiments indicated that the release of the Phl-4B cocrystal followed Fick diffusion. The stability activity of phloretin after pharmaceutical cocrystallization was improved. The antioxidant of the Phl-4B cocrystal was better than that of pure Phl.

Analysis of the Dissolution Behavior of Theophylline and Its Cocrystal Using ATR-FTIR Spectroscopic Imaging

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging is a powerful tool to visualize the distribution of components, and it has been used to analyze drug release from tablets. In this work, ATR-FTIR spectroscopic imaging was applied for observing the dissolution of molecular crystals from tablet compacts. The IR spectra provided chemically specific information about the transformation of crystal structures during the dissolution experiments. Theophylline (TPL) anhydrate and its cocrystals were used as model systems of molecular crystals. The IR spectra during the dissolution of TPL revealed information about the crystal structure of TPL, which transformed from anhydrate to monohydrate in water. During a dissolution test of a model cocrystal system, it was suggested that an active pharmaceutical ingredient (API) and a coformer were dissolved in water simultaneously. The IR spectra that were acquired during the dissolution of a cocrystal tablet showed new spectral bands attributed to the API after 5 min. This suggested that the precipitation of API was observed during the dissolution experiment. Measurements from ATR-FTIR spectroscopic imaging can visualize the drug release from the tablet and determine the transformation of molecular crystals during their dissolution. These results will have an impact on clarifying the dissolution mechanism of molecular crystals.

Synthesis and structural investigation of salts of 2-amino-3-methylpyridine with carboxylic acid derivatives: an experimental and theoretical study

The salts bis(2-amino-3-methylpyridinium) fumarate dihydrate, 2C6H9N2+·C4H2O22-·2H2O (I), and 2-amino-3-methylpyridinium 5-chlorosalicylate, C6H9N2+·C7H4ClO3- (II), were synthesized from 2-amino-3-methylpyridine with fumaric acid and 5-chlorosalicylic acid, respectively. The crystal structures of these salts were characterized by single-crystal X-ray diffraction, revealing protonation in I and II by the transfer of a H atom from the acid to the pyridine base. In the crystals of both I and II, N-H...O interactions form an R22(8) ring motif. Hirshfeld surface analysis distinguishes the interactions present in the crystal structures of I and II, and the two-dimensional (2D) fingerprint plot analysis shows the percentage contribution of each type of interaction in the crystal packing. The volumes of the crystal voids of I (39.65 Å3) and II (118.10 Å3) have been calculated and reveal that the crystal of I is more mechanically stable than II. Frontier molecular orbital (FMO) analysis predicts that the band gap energy of II (2.6577 eV) is lower compared to I (4.0035 eV). The Quantum Theory of Atoms In Molecules (QTAIM) analysis shows that the pyridinium-carboxylate N-H...O interaction present in I is stronger than the other interactions, whereas in II, the hydroxy-carboxylate O-H...O interaction is stronger than the pyridinium-carboxylate N-H...O interaction; the bond dissociation energies also confirm these results. The positive Laplacian [∇2ρ(r) > 0] of these interactions shows that the interactions are of the closed shell type. An in-silico ADME (Absorption, Distribution, Metabolism and Excretion) study predicts that both salts will exhibit good pharmacokinetic properties and druglikeness.

Drug Crystal Precipitation in Biorelevant Bicarbonate Buffer: A Well-Controlled Comparative Study with Phosphate Buffer

The purpose of the present study was to clarify whether the precipitation profile of a drug in bicarbonate buffer (BCB) may differ from that in phosphate buffer (PPB) by a well-controlled comparative study. The precipitation profiles of structurally diverse poorly soluble drugs in BCB and PPB were evaluated by a pH-shift precipitation test or a solvent-shift precipitation test (seven weak acid drugs (pKa: 4.2 to 7.5), six weak base drugs (pKa: 4.8 to 8.4), one unionizable drug, and one zwitterionic drug). To focus on crystal precipitation processes, each ionizable drug was first completely dissolved in an HCl (pH 3.0) or NaOH (pH 11.0) aqueous solution (450 mL, 50 rpm, 37 °C). A 10-fold concentrated buffer solution (50 mL) was then added to shift the pH value to 6.5 to initiate precipitation (final volume: 500 mL, buffer capacity (β): 4.4 mM/ΔpH (BCB: 10 mM or PPB: 8 mM), ionic strength (I): 0.14 M (adjusted by NaCl)). The pH, β, and I values were set to be relevant to the physiology of the small intestine. For an unionizable drug, a solvent-shift method was used (1/100 dilution). To maintain the pH value of BCB, a floating lid was used to avoid the loss of CO2. The floating lid was applied also to PPB to precisely align the experimental conditions between BCB and PPB. The solid form of the precipitants was identified by powder X-ray diffraction and differential scanning microscopy. The precipitation of weak acids (pKa ≤ 5.1) and weak bases (pKa ≥ 7.3) was found to be slower in BCB than in PPB. In contrast, the precipitation profiles in BCB and PPB were similar for less ionizable or nonionizable drugs at pH 6.5. The final pH values of the bulk phase were pH 6.5 ± 0.1 after the precipitation tests in all cases. All precipitates were in their respective free forms. The precipitation of ionizable weak acids and bases was slower in BCB than in PPB. The surface pH of precipitating particles may have differed between BCB and PPB due to the slow hydration process of CO2 specific to BCB. Since BCB is a physiological buffer in the small intestine, it should be considered as an option for precipitation studies of ionizable weak acids and bases.

Spherical Crystallization Based on Liquid-Liquid Phase Separation in a Reverse Antisolvent Crystallization Process

Vanillin crystals undergo needle-like morphology that results in poor flowability, crystal breakage, and low packing density. The spherical crystallization technology can produce particles with improved flowability and stability. A reverse antisolvent crystallization based on liquid-liquid phase separation is proposed in this work to produce vanillin spherical agglomerates. Hansen Solubility Parameters are applied to explain the liquid-liquid phase separation (LLPS) phenomenon. The Pixact Crystallization Monitoring system is applied to in-situ monitor the whole process. A six-step spherical crystallization mechanism is revealed based on the recorded photos, including the generation of oil droplets, nucleation inside oil droplets, the coalescence and split of oil droplets, crystal growth and agglomeration, breakage of oil droplets, and attrition of agglomerates. Different working conditions are tested to explore the best operation parameters and a frequency-conversion stirring strategy is proposed to improve the production of spherical crystals.

Efficient Screening of Pharmaceutical Cocrystals by Microspacing In-Air Sublimation

Cocrystal screening and single-crystal growth remain the primary obstacles in the development of pharmaceutical cocrystals. Here, we present a new approach for cocrystal screening, microspacing in-air sublimation (MAS), to obtain new cocrystals and grow high-quality single crystals of cocrystals within tens of minutes. The method possesses the advantages of strong designable ability of devices, user-friendly control, and compatibility with materials, especially for the thermolabile molecules. A novel drug-drug cocrystal of favipiravir (FPV) with salicylamide (SAA) was first discovered by this method, which shows improved physiochemical properties. Furthermore, this method proved effective in cultivating single crystals of FPV-isonicotinamide (FPV-INIA), FPV-urea, FPV-nicotinamide (FPV-NIA), and FPV-tromethamine (FPV-Tro) cocrystals, and the structures of these cocrystals were determined for the first time. By adjusting the growth temperature and growth distance precisely, we also achieved single crystals of 10 different paracetamol (PCA) cocrystals and piracetam (PIR) cocrystals, which underscores the versatility and efficiency of this method in pharmaceutical cocrystal screening.

Co-Processed Crystalline Solids of Ivermectin with Span® 60 as Solubility Enhancers of Ivermectin in Natural Oils

Despite being discovered over five decades ago, little is still known about ivermectin. Ivermectin has several physico-chemical properties that can result in it having poor bioavailability. In this study, polymorphic and co-crystal screening was used to see if such solid-state modifications can improve the oil solubility of ivermectin. Span® 60, a lipophilic non-ionic surfactant, was chosen as co-former. The rationale behind attempting to improve oil solubility was to use ivermectin in future topical and transdermal preparations to treat a range of skin conditions like scabies and head lice. Physical mixtures were also prepared in the same molar ratios as the co-crystal candidates, to serve as controls. Solid-state characterization was performed using X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The FTIR spectra of the co-crystal candidates showed the presence of Span® 60's alkyl chain peaks, which were absent in the spectra of the physical mixtures. Due to the absence of single-crystal X-ray data, co-crystal formation could not be confirmed, and therefore these co-crystal candidates were referred to as co-processed crystalline solids. Following characterization, the solid-state forms, physical mixtures and ivermectin raw material were dissolved in natural penetration enhancers, i.e., avocado oil (AVO) and evening primrose oil (EPO). The co-processed solids showed increased oil solubility by up to 169% compared to ivermectin raw material. The results suggest that co-processing of ivermectin with Span® 60 can be used to increase its oil solubility and can be useful in the development of oil-based drug formulations.

Comprehensive Application of XFEL Microcrystallography for Challenging Targets in Various Organic Compounds

There is a growing demand for structure determination from small crystals, and the three-dimensional electron diffraction (3D ED) technique can be employed for this purpose. However, 3D ED has certain limitations related to the crystal thickness and data quality. We here present the application of serial X-ray crystallography (SX) with X-ray free electron lasers (XFELs) to small (a few μm or less) and thin (a few hundred nm or less) crystals of novel compounds dispersed on a substrate. For XFEL exposures, two-dimensional (2D) scanning of the substrate coupled with rotation enables highly efficient data collection. The recorded patterns can be successfully indexed using lattice parameters obtained through 3D ED. This approach is especially effective for challenging targets, including pharmaceuticals and organic materials that form preferentially oriented flat crystals in low-symmetry space groups. Some of these crystals have been difficult to solve or have yielded incomplete solutions using 3D ED. Our extensive analyses confirmed the superior quality of the SX data regardless of crystal orientations. Additionally, 2D scanning with XFEL pulses gives an overall distribution of the samples on the substrate, which can be useful for evaluating the properties of crystal grains and the quality of layered crystals. Therefore, this study demonstrates that XFEL crystallography has become a powerful tool for conducting structure studies of small crystals of organic compounds.

Mechanoresponsive Flexible Crystals

Flexible crystals have gained significant attention owing to their remarkable pliability, plasticity, and adaptability, making them highly popular in various research and application fields. The main challenges in developing flexible crystals lie in the rational design, preparation, and performance optimization of such crystals. Therefore, a comprehensive understanding of the fundamental origins of crystal flexibility is crucial for establishing evaluation criteria and design principles. This Perspective offers a retrospective analysis of the development of flexible crystals over the past two decades. It summarizes the elastic standards and possible plastic bending mechanisms tailored to diverse flexible crystals and analyzes the assessment of their theoretical basis and applicability. Meanwhile, the compatibility between crystal elasticity and plasticity has been discussed, unveiling the immense prospects of elastic/plastic crystals for applications in biomedicine, flexible electronic devices, and flexible optics. Furthermore, this Perspective presents state-of-the-art experimental avenues and analysis methods for investigating molecular interactions in molecular crystals, which is vital for the future exploration of the mechanisms of crystal flexibility.

Advancing Drug Delivery Paradigms: Polyvinyl Pyrolidone (PVP)-Based Amorphous Solid Dispersion for Enhanced Physicochemical Properties and Therapeutic Efficacy

BACKGROUND

The current challenge in drug development lies in addressing the physicochemical issues that lead to low drug effectiveness. Solubility, a crucial physicochemical parameter, greatly influences various biopharmaceutical aspects of a drug, including dissolution rate, absorption, and bioavailability. Amorphous solid dispersion (ASD) has emerged as a widely explored approach to enhance drug solubility.

OBJECTIVE

The objective of this review is to discuss and summarize the development of polyvinylpyrrolidone (PVP)-based amorphous solid dispersion in improving the physicochemical properties of drugs, with a focus on the use of PVP as a novel approach.

METHODOLOGY

This review was conducted by examining relevant journals obtained from databases such as Scopus, PubMed, and Google Scholar, since 2018. The inclusion and exclusion criteria were applied to select suitable articles.

RESULTS

This study demonstrated the versatility and efficacy of PVP in enhancing the solubility and bioavailability of poorly soluble drugs. Diverse preparation methods, including solvent evaporation, melt quenching, electrospinning, coprecipitation, and ball milling are discussed for the production of ASDs with tailored characteristics.

CONCLUSION

PVP-based ASDs could offer significant advantages in the formulation strategies, stability, and performance of poorly soluble drugs to enhance their overall bioavailability. The diverse methodologies and findings presented in this review will pave the way for further advancements in the development of effective and tailored amorphous solid dispersions.

Investigation into polymorphism within ethenzamide-ethylmalonic acid cocrystal using Raman and terahertz vibrational spectroscopy

Two cocrystal polymorphs of ethenzamide (ETZ) and ethylmalonic acid (EMA) were synthesized by solvent evaporation. Crystal structure analysis revealed that the main amide - carboxyl heterosynthon in ETZ-EMA cocrystal Form I and Form II are the same, but the crystal structure of these two polymorphs are different. Terahertz (THz) and Raman vibrational spectroscopy were used to characterize ETZ, EMA, ETZ-EMA cocrystal polymorph Form I and Form II respectively. The experimental results showed that ETZ, EMA, ETZ-EMA cocrystal Form I and ETZ-EMA cocrystal Form II exhibited completely different characteristic peaks. Both THz and Raman vibrational spectroscopy can be used to distinguish ETZ-EMA cocrystal Form I from Form II. Furthermore, the investigation of phase transition induced by temperature and solid-state grinding was also performed. In the temperature phase transition experiments, when the powder sample was heated to a temperature range of 80-82 °C, the metastable ETZ-EMA cocrystal Form I transformed into the more stable ETZ-EMA cocrystal Form II. Solid-state grinding analysis revealed that the results of the ETZ-EMA cocrystal polymorph synthesis in grinding experiments depended on the polarity of the solvents used. Grinding without solvent or with high polarity solvents tended to result in the stable ETZ-EMA cocrystal Form II. Moreover, the metastable ETZ-EMA cocrystal Form I would transform into Form II after further grinding process. These results demonstrate that THz and Raman vibrational spectroscopy have high sensitivity and accuracy in the detection of both cocrystal synthesis and cocrystal polymorph phase transitions.

New Drug Delivery Systems for Stable Oral Absorption: Theory, Strategies, and Applications

The oral dosage route still remains the most common and preferred route for drug administration due to convenient handling, high patient compliance, and cost-effectiveness. However, the oral absorption of drugs can be a complex process depending upon: (i) physicochemical properties of the drug (e.g., pKa, lipophilicity, solubility), (ii) pharmaceutical factors (e.g., dosage form), and (iii) physiological factors (e.g., gastrointestinal pH values, gastric emptying rate, gastric and intestinal pH, metabolism). Oral administration of drugs sometimes leads to poor and/or variable oral bioavailability, possible leading to unstable clinical outcomes. To offer stable and improved pharmacokinetic behavior of drugs, a number of formulation approaches have been developed with a focus on enhancement of the solubility, dissolution rate, and oral bioavailability of drugs. To provide new formulation platforms for better and safe medication, it is considered essential to understand the physicochemical, biochemical, metabolic, and biological barriers which limit overall drug bioavailability in more detail. The review article considers several crucial factors affecting oral absorption of drug substances. This article also describes the recent progress in formulation approaches to achieve stable and improved biopharmaceutical properties of orally-taken drugs.

Overview and thermodynamic modelling of deep eutectic solvents as co-solvents to enhance drug solubilities in water

The poor water solubility of active pharmaceutical ingredients (APIs) is a major challenge in the pharmaceutical industry. Co-solvents are sometimes added to enhance drug dissolution. A novel group of co-solvents, the Deep Eutectic Solvents (DES), have gained interest in the pharmaceutical field due to their good solvent power, biodegradability, sustainability, non-toxicity, and low cost. In this study, we first provide an overview of all the literature solubility studies involving a drug or API + water + DES, which can be a valuable list to some researchers. Then, we analyze these systems with focus on each individual drug/API and provide statistical information on each. A similar analysis is carried out with focus on the individual DESs. An investigation of the numeric values of the water-solubility enhancement by the different DESs for various drugs indicates that DESs are indeed effective co-solvents, with varying degrees of solubility enhancement, even up to 15-fold. This is strongly encouraging, indicating the need for further studies to find the most promising DESs for solubility enhancement. However, time-consuming and costly trial and error should be prevented by first screening, using theoretical-based or thermodynamic-based models. Based on this conclusion, the second part of the study is concerned with investigating and suggesting accurate thermodynamic approaches to tackle the phase equilibrium modeling of such systems. For this purpose, a large data bank was collected, consisting of 2009 solubility data of 25 different drugs/APIs mixed with water and 31 different DESs as co-solvents at various DES concentrations, over wide ranges of temperatures at atmospheric pressure. This data bank includes 107 DES + water + drug/API systems in total. The solubility data were then modeled according to the solid-liquid equilibrium framework, using the local composition activity coefficient models of NRTL, and UNIQUAC. The results showed acceptable behavior with respect to the experimental values and trends for all of the investigated systems, with AARD% values of 9.65 % and 14.08 % for the NRTL and UNIQUAC models, respectively. In general, the lower errors of NRTL, as well as its simpler calculation process and the requirement of fewer component parameters, suggest the priority of NRTL over UNIQUAC for use in this field.

ADMET and Solubility Analysis of New 5-Nitroisatine-Based Inhibitors of CDK2 Enzymes

The development of new substances with the ability to interact with a biological target is only the first stage in the process of the creation of new drugs. The 5-nitroisatin derivatives considered in this study are new inhibitors of cyclin-dependent kinase 2 (CDK2) intended for anticancer therapy. The research, carried out based on the ADMET (absorption, distribution, metabolism, excretion, toxicity) methods, allowed a basic assessment of the physicochemical parameters of the tested drugs to be made. The collected data clearly showed the good oral absorption, membrane permeability, and bioavailability of the tested substances. The analysis of the metabolite activity and toxicity of the tested drugs did not show any critical hazards in terms of the toxicity of the tested substances. The substances' low solubility in water meant that extended studies tested compounds were required, which helped to select solvents with a high dissolving capacity of the examined substances, such as DMSO or NMP. The use of aqueous binary mixtures based on these two solvents allowed a relatively high solubility with significantly reduced toxicity and environmental index compared to pure solvents to be maintained, which is important in the context of the search for green solvents for pharmaceutical use.

Saquinavir-Piperine Eutectic Mixture: Preparation, Characterization, and Dissolution Profile

The dissolution rate of the anti-HIV drug saquinavir base (SQV), a poorly water-soluble and extremely low absolute bioavailability drug, was improved through a eutectic mixture formation approach. A screening based on a liquid-assisted grinding technique was performed using a 1:1 molar ratio of the drug and the coformers sodium saccharinate, theobromine, nicotinic acid, nicotinamide, vanillin, vanillic acid, and piperine (PIP), followed by differential scanning calorimetry (DSC). Given that SQV-PIP was the only resulting eutectic system from the screening, both the binary phase and the Tammann diagrams were adapted to this system using DSC data of mixtures prepared from 0.1 to 1.0 molar ratios in order to determine the exact eutectic composition. The SQV-PIP system formed a eutectic at a composition of 0.6 and 0.40, respectively. Then, a solid-state characterization through DSC, powder X-ray diffraction (PXRD), including small-angle X-ray scattering (SAXS) measurements to explore the small-angle region in detail, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a powder dissolution test were performed. The conventional PXRD analyses suggested that the eutectic mixture did not exhibit structural changes; however, the small-angle region explored through the SAXS instrument revealed a change in the crystal structure of one of their components. FT-IR spectra showed no molecular interaction in the solid state. Finally, the dissolution profile of SQV in the eutectic mixture was different from the dissolution of pure SQV. After 45 min, approximately 55% of the drug in the eutectic mixture was dissolved, while, for pure SQV, 42% dissolved within this time. Hence, this study concludes that the dissolution rate of SQV can be effectively improved through the approach of using PIP as a coformer.

Cocrystals Enhance Biopharmaceutical and Antimicrobial Properties of Norfloxacin

A solvate cocrystal of the antimicrobial norfloxacin (NFX) was formed by using isonicotinamide (INA) as a coformer with the solvent evaporation technique. The cocrystal formation was confirmed by performing solid-state characterization techniques. We evaluated the dissolution under supersaturated conditions and also the solubility at the vertex of triphasic domain of cocrystal and NFX in both water and Fasted-State Simulated Intestinal Fluid (FaSSIF). The antimicrobial activity was evaluated using the microdilution technique. The cocrystal showed 1.8 times higher dissolution than NFX in water at 60 min and 1.3 times higher in FaSSIF at 180 min in the kinetic study. The cocrystal also had an increase in solubility of 8.38 times in water and 6.41 times in FaSSIF. The biopharmaceutical properties of NFX with cocrystallization improved antimicrobial action, as shown in the results of minimum inhibitory concentration (MIC) and inhibitory concentrations of 50% (IC50%) and 90% (IC90%). This paper presents, for the first time, a more in-depth analysis of the cocrystal of NFX-INA concerning its dissolution, solubility, and antimicrobial activity. In all these criteria, the cocrystal obtained better results compared to the pure drug.

Recent Advances in Co-Former Screening and Formation Prediction of Multicomponent Solid Forms of Low Molecular Weight Drugs

Multicomponent solid forms of low molecular weight drugs, such as co-crystals, salts, and co-amorphous systems, are a result of the combination of an active pharmaceutical ingredient (API) with a pharmaceutically acceptable co-former. These solid forms can enhance the physicochemical and pharmacokinetic properties of APIs, making them increasingly interesting and important in recent decades. Nevertheless, predicting the formation of API multicomponent solid forms in the early stages of formulation development can be challenging, as it often requires significant time and resources. To address this, empirical and computational methods have been developed to help screen for potential co-formers more efficiently and accurately, thus reducing the number of laboratory experiments needed. This review provides a comprehensive overview of current screening and prediction methods for the formation of API multicomponent solid forms, covering both crystalline states (co-crystals and salts) and amorphous forms (co-amorphous). Furthermore, it discusses recent advances and emerging trends in prediction methods, with a particular focus on artificial intelligence.

Amorphous Solid Dispersion as Drug Delivery Vehicles in Cancer

Cancer treatment has improved over the past decades, but a major challenge lies in drug formulation, specifically for oral administration. Most anticancer drugs have poor water solubility which can affect their bioavailability. This causes suboptimal pharmacokinetic performance, resulting in limited efficacy and safety when administered orally. As a result, it is essential to develop a strategy to modify the solubility of anticancer drugs in oral formulations to improve their efficacy and safety. A promising approach that can be implemented is amorphous solid dispersion (ASD) which can enhance the aqueous solubility and bioavailability of poorly water-soluble drugs. The addition of a polymer can cause stability in the formulations and maintain a high supersaturation in bulk medium. Therefore, this study aimed to summarize and elucidate the mechanisms and impact of an amorphous solid dispersion system on cancer therapy. To gather relevant information, a comprehensive search was conducted using keywords such as "anticancer drug" and "amorphous solid dispersion" in the PubMed, Scopus, and Google Scholar databases. The review provides an overview and discussion of the issues related to the ASD system used to improve the bioavailability of anticancer drugs based on molecular pharmaceutics. A thorough understanding of anticancer drugs in this system at a molecular level is imperative for the rational design of the products.

Ternary Solid Dispersions: A Review of the Preparation, Characterization, Mechanism of Drug Release, and Physical Stability

The prevalence of active pharmaceutical ingredients (APIs) with low water solubility has experienced a significant increase in recent years. These APIs present challenges in formulation, particularly for oral dosage forms, despite their considerable therapeutic potential. Therefore, the improvement of solubility has become a major concern for pharmaceutical enterprises to increase the bioavailability of APIs. A promising formulation approach that can effectively improve the dissolution profile and the bioavailability of poorly water-soluble drugs is the utilization of amorphous systems. Numerous formulation methods have been developed to enhance poorly water-soluble drugs through amorphization systems, including co-amorphous formulations, amorphous solid dispersions (ASDs), and the use of mesoporous silica as a carrier. Furthermore, the successful enhancement of certain drugs with poor aqueous solubility through amorphization has led to their incorporation into various commercially available preparations, such as ASDs, where the crystalline structure of APIs is transformed into an amorphous state within a hydrophilic matrix. A novel approach, known as ternary solid dispersions (TSDs), has emerged to address the solubility and bioavailability challenges associated with amorphous drugs. Meanwhile, the introduction of a third component in the ASD and co-amorphous systems has demonstrated the potential to improve performance in terms of solubility, physical stability, and processability. This comprehensive review discusses the preparation and characterization of poorly water-soluble drugs in ternary solid dispersions and their mechanisms of drug release and physical stability.

Finding the Right Solvent: A Novel Screening Protocol for Identifying Environmentally Friendly and Cost-Effective Options for Benzenesulfonamide

This study investigated the solubility of benzenesulfonamide (BSA) as a model compound using experimental and computational methods. New experimental solubility data were collected in the solvents DMSO, DMF, 4FM, and their binary mixtures with water. The predictive model was constructed based on the best-performing regression models trained on available experimental data, and their hyperparameters were optimized using a newly developed Python code. To evaluate the models, a novel scoring function was formulated, considering not only the accuracy but also the bias-variance tradeoff through a learning curve analysis. An ensemble approach was adopted by selecting the top-performing regression models for test and validation subsets. The obtained model accurately back-calculated the experimental data and was used to predict the solubility of BSA in 2067 potential solvents. The analysis of the entire solvent space focused on the identification of solvents with high solubility, a low environmental impact, and affordability, leading to a refined list of potential candidates that meet all three requirements. The proposed procedure has general applicability and can significantly improve the quality and speed of experimental solvent screening.

Exploring the Solubility and Bioavailability of Sodium Salt and Its Free Acid Solid Dispersions of Dolutegravir

Amorphous salt solid dispersion (ASSD) of Dolutegravir amorphous salt (DSSD) was generated using quench cooling and compared to its Dolutegravir free acid solid dispersion (DFSD) to improve the solubility and bioavailability. Soluplus (SLP) was used as a polymeric carrier in both solid dispersions. The prepared DSSD and DFSD, physical mixtures, and individual compounds were characterized by employing DSC, XRPD, and FTIR to assess the formation of the single homogenous amorphous phase and the existence of intermolecular interactions. Partial crystallinity was observed for DSSD, unlike DFSD, which is completely amorphous. No intermolecular interactions were observed between the Dolutegravir sodium (DS)/Dolutegravir free acid (DF) and SLP from the FTIR spectra of DSSD and DFSD. Both DSSD and DFSD improved the solubility of Dolutegravir (DTG) to 5.7 and 4.54 folds compared to the pure forms. Similarly, drug release from DSSD and DFSD was 2 and 1.5 folds higher than that in the pure form, owing to the rapid dissolution of the drug from the formulations. The permeability of DSSD and DFSD was estimated using the dialysis membrane, which enhanced the DTG permeability. The improvement in in vitro studies was translated into in vivo pharmacokinetic profiles of DSSD and DFSD, where 4.0 and 5.6 folds, respectively, improved the C_max of DTG.

Synthesis and characterization of innovative resveratrol nanobelt-like particles and assessment of their bioactivity, antioxidative and antibacterial properties

Recently, many studies have shown various beneficial effects of polyphenol resveratrol (Res) on human health. The most important of these effects include cardioprotective, neuroprotective, anti-cancer, anti-inflammatory, osteoinductive, and anti-microbial effects. Resveratrol has cis and trans isoforms, with the trans isoform being more stable and biologically active. Despite the results of in vitro experiments, resveratrol has limited potential for application in vivo due to its poor water solubility, sensitivity to oxygen, light, and heat, rapid metabolism, and therefore low bioavailability. The possible solution to overcome these limitations could be the synthesis of resveratrol in nanoparticle form. Accordingly, in this study, we have developed a simple, green solvent/non-solvent physicochemical method to synthesize stable, uniform, carrier-free resveratrol nanobelt-like particles (ResNPs) for applications in tissue engineering. UV-visible spectroscopy (UV-Vis) was used to identify the trans isoform of ResNPs which remained stable for at least 63 days. The additional qualitative analysis was performed by Fourier transform infrared spectroscopy (FTIR), while X-ray diffraction (XRD) determined the monoclinic structure of resveratrol with a significant difference in the intensity of diffraction peaks between commercial and nano-belt form. The morphology of ResNPs was evaluated by optical microscopy and field-emission scanning electron microscope (FE-SEM) that revealed a uniform nanobelt-like structure with an individual thickness of less than 1 μm. Bioactivity was confirmed using Artemia salina in vivo toxicity assay, while 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH) reduction assay showed the good antioxidative potential of concentrations of 100 μg/ml and lower. Microdilution assay on several reference strains and clinical isolates showed promising antibacterial potential on Staphylococci, with minimal inhibitory concentration (MIC) being 800 μg/ml. Bioactive glass-based scaffolds were coated with ResNPs and characterized to confirm coating potential. All of the above make these particles a promising bioactive, easy-to-handle component in various biomaterial formulations.

Phosphate buffer interferes dissolution of prazosin hydrochloride in compendial dissolution testing

The purpose of this study was to elucidate the lack of supersaturation behavior in the dissolution profile of prazosin hydrochloride (PRZ-HCl) in the compendial dissolution test. The equilibrium solubility was measured by a shake-flask method. Dissolution tests were performed by a compendial paddle method with a phosphate buffer solution (pH 6.8, 50 mM phosphate). The solid form of the residual particles was identified by Raman spectroscopy. In the pH range below 6.5, the equilibrium solubility in phosphate buffer was lower than that in the unbuffered solutions (pH adjusted by HCl and NaOH). Raman spectra showed that the residual solid was a phosphate salt of PRZ. In the pH range above 6.5, the pH-solubility profiles in the phosphate buffer solutions and the unbuffered solutions were the same. The residual solid was a PRZ freebase (PRZ-FB). In the dissolution test, PRZ-HCl particles first changed to a phosphate salt within 5 min, then gradually changed to PRZ-FB after several hours. Since the intestinal fluid is buffered by the bicarbonate system in vivo, the dissolution behavior in vivo may not be properly evaluated using a phosphate buffer solution. For drugs with a low phosphate solubility product, it is necessary to consider this aspect.

Cocrystal Synthesis through Crystal Structure Prediction

Crystal structure prediction (CSP) is an invaluable tool in the pharmaceutical industry because it allows to predict all the possible crystalline solid forms of small-molecule active pharmaceutical ingredients. We have used a CSP-based cocrystal prediction method to rank ten potential cocrystal coformers by the energy of the cocrystallization reaction with an antiviral drug candidate, MK-8876, and a triol process intermediate, 2-ethynylglyclerol. For MK-8876, the CSP-based cocrystal prediction was performed retrospectively and successfully predicted the maleic acid cocrystal as the most likely cocrystal to be observed. The triol is known to form two different cocrystals with 1,4-diazabicyclo[2.2.2]octane (DABCO), but a larger solid form landscape was desired. CSP-based cocrystal screening predicted the triol-DABCO cocrystal as rank one, while a triol-l-proline cocrystal was predicted as rank two. Computational finite-temperature corrections enabled determination of relative crystallization propensities of the triol-DABCO cocrystals with different stoichiometries and prediction of the triol-l-proline polymorphs in the free-energy landscape. The triol-l-proline cocrystal was obtained during subsequent targeted cocrystallization experiments and was found to exhibit an improved melting point and deliquescence behavior over the triol-free acid, which could be considered as an alternative solid form in the synthesis of islatravir.

Levocetirizine-Loaded Electrospun Fibers from Water-Soluble Polymers: Encapsulation and Drug Release

Electrospun fibers containing levocetirizine, a BCS III drug, were prepared from three water-soluble polymers, hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA). Fiber-spinning technology was optimized for each polymer separately. The polymers contained 10 wt% of the active component. An amorphous drug was homogeneously distributed within the fibers. The solubility of the drug in the polymers used was limited, with a maximum of 2.0 wt%, but it was very large in most of the solvents used for fiber spinning and in the dissolution media. The thickness of the fibers was uniform and the presence of the drug basically did not influence it at all. The fiber diameters were in the same range, although somewhat thinner fibers could be prepared from PVA than from the other two polymers. The results showed that the drug was amorphous in the fibers. Most of the drug was located within the fibers, probably as a separate phase; the encapsulation efficiency proved to be 80-90%. The kinetics of the drug release were evaluated quantitatively by the Noyes-Whitney model. The released drug was approximately the same for all the polymers under all conditions (pH), and it changed somewhere between 80 and 100%. The release rate depended both on the type of polymer and pH and varied between 0.1 and 0.9 min^-1. Consequently, the selection of the carrier polymer allowed for the adjustment of the release rate according to the requirements, thus justifying the use of electrospun fibers as carrier materials for levocetirizine.

Antisolvent Crystallization of Telmisartan Using Stainless-Steel Micromixing Membrane Contactors

Controlled continuous crystallization of the active pharmaceutical ingredient (API) telmisartan (TEL) has been conducted from TEL/DMSO solutions by antisolvent crystallization in deionized water using membrane micromixing contactors. The purpose of this work was to test stainless-steel membranes with ordered 10 μm pores spaced at 200 μm in a stirred-cell (batch, LDC-1) and crossflow (continuous, AXF-1) system for TEL formation. By controlling the feed flow rate of the API and solvent, through the membrane pores as well as the antisolvent flow, it was possible to tightly control the micromixing and with that to control the crystal nucleation and growth. Batch crystallization without the membrane resulted in an inhomogeneous crystallization process, giving a mixture of crystalline and amorphous TEL materials. The rate of crystallization was controlled with a higher DMSO content (4:1 DMSO/DI water), resulting in slower crystallization of the TEL material. Both membrane setups, stirred batch and the crossflow, yielded the amorphous TEL particles when deionized water was used, while a crystalline material was produced when a mixture of DI water and DMSO was used.

Preparation and characterization of naproxen solid dispersion using different hydrophilic carriers and in-vivo evaluation of its analgesic activity in mice

Background

Solid dispersion (SD) has been used conventionally as a successful technique for improving the dissolution profile and bioavailability of poorly water-soluble drugs. The aim of this study was to progress the dissolution rate and bioavailability of naproxen (BCS class II) by SD technique.

Materials & methods

In this study, hydrophilic carriers are used for preparing solid dispersion of naproxen by evaporation method. The prepared optimized SDNs were evaluated by in-vitro drug dissolution test, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The in-vivo analgesic effects tests of the optimized SDNs (SDN-2 and SDN-5) were performed by tail immersion method and writhing method.

Results

All the prepared SDNs exhibited a significant increase in the dissolution of naproxen compared to that of the pure drug. Among them, SDN-2 (the dispersion with sodium starch glycolate at 1:2 ratio of naproxen and sodium starch glycolate) and SDN-5 (using the combination of PEG-8000 and sodium starch glycolate with naproxen at 1:1:1 ratio) showed faster dissolution rate as compared to other solid dispersions (SDNs) and pure naproxen. SDN-2 showed 5.4 times better dissolution rate and SDN-5 depicted 6.5-fold increment of dissolution rate compared to pure naproxen drug. DSC, PXRD and SEM microscopy showed that the drugs crystallinity was decreased during the preparation process. FTIR study revealed that naproxen was stable in polymeric dispersions and there was no interaction among the drug and polymers. In writhing method, the percentage inhibition of the number of writhes showed significantly greater (p < 0.01), (p < 0.0001) analgesic activity for the higher dose treatment groups SDN-2(H), and SDN-5(H), respectively, when contrasted to the pure drug naproxen. For tail immersion test, there is increase in latency time at 90 min which is significantly greater (P < 0.01), (P < 0.05), (P < 0.01) for treatment groups SDN-2(H), SDN-5(L), and SDN-5(H), respectively that ultimately authenticates that the optimized SDNs (SDN-2, SDN-5) showed better analgesic activity in mice in comparison with the pure drug.

Conclusion

It can be concluded that dissolution of the naproxen could be improved by the making solid dispersion using sodium starch glycolate and/or combination of sodium starch glycolate and PEG 8000 due to the complete transformation of drug into amorphous form with the entire loss of crystallinity, as evidenced by DSC, PXRD, and SEM and also consequences the enhanced analgesic activity in mice.

Advancement in Solubilization Approaches: A Step towards Bioavailability Enhancement of Poorly Soluble Drugs

A drug's aqueous solubility is defined as the ability to dissolve in a particular solvent, and it is currently a major hurdle in bringing new drug molecules to the market. According to some estimates, up to 40% of commercialized products and 70-90% of drug candidates in the development stage are poorly soluble, which results in low bioavailability, diminished therapeutic effects, and dosage escalation. Because of this, solubility must be taken into consideration when developing and fabricating pharmaceutical products. To date, a number of approaches have been investigated to address the problem of poor solubility. This review article attempts to summarize several conventional methods utilized to increase the solubility of poorly soluble drugs. These methods include the principles of physical and chemical approaches such as particle size reduction, solid dispersion, supercritical fluid technology, cryogenic technology, inclusion complex formation techniques, and floating granules. It includes structural modification (i.e., prodrug, salt formation, co-crystallization, use of co-solvents, hydrotrophy, polymorphs, amorphous solid dispersions, and pH variation). Various nanotechnological approaches such as liposomes, nanoparticles, dendrimers, micelles, metal organic frameworks, nanogels, nanoemulsions, nanosuspension, carbon nanotubes, and so forth have also been widely investigated for solubility enhancement. All these approaches have brought forward the enhancement of the bioavailability of orally administered drugs by improving the solubility of poorly water-soluble drugs. However, the solubility issues have not been completely resolved, owing to several challenges associated with current approaches, such as reproducibility in large scale production. Considering that there is no universal approach for solving solubility issues, more research is needed to simplify the existing technologies, which could increase the number of commercially available products employing these techniques.