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.

Optimizing Drug Development: Harnessing the Sustainability of Pharmaceutical Cocrystals

Environmental impacts of the industrial revolution necessitate adoption of sustainable practices in all areas of development. The pharmaceutical industry faces increasing pressure to minimize its ecological footprint due to its significant contribution to environmental pollution. Over the past two decades, pharmaceutical cocrystals have received immense popularity due to their ability to optimize the critical attributes of active pharmaceutical ingredients and presented an avenue to bring improved drug products to the market. This review explores the potential of pharmaceutical cocrystals as an ecofriendly alternative to traditional solid forms, offering a sustainable approach to drug development. From reducing the number of required doses to improving the stability of actives, from eliminating synthetic operations to using pharmaceutically approved chemicals, from the use of continuous and solvent-free manufacturing methods to leveraging published data on the safety and toxicology, the cocrystallization approach contributes to sustainability of drug development. The latest trends suggest a promising role of pharmaceutical cocrystals in bringing novel and improved medicines to the market, which has been further fuelled by the recent guidance from the major regulatory agencies.

Development of direct compression Acetazolamide tablet with improved bioavailability in healthy human volunteers enabled by cocrystallization with p-Aminobenzoic acid

Pharmaceutical cocrystallization has been widely used to improve physicochemical properties of APIs. However, developing cocrystal formulation with proven clinical success remains scarce. Successful translation of a cocrystal to suitable dosage forms requires simultaneously improvement of several deficient physicochemical properties over the parent API, without deteriorating other properties critical for successful product development. In the present work, we report the successful development of a direct compression tablet product of acetazolamide (ACZ), using a 1:1 cocrystal of acetazolamide with p-aminobenzoic acid (ACZ-PABA). The ACZ-PABA tablet exhibits superior biopharmaceutical performance against the commercial tablet, DIAMOX® (250 mg), in healthy human volunteers, leading to more than 50 % reduction in the required dose.

A Review of Coformer Utilization in Multicomponent Crystal Formation

Most recently discovered active pharmaceutical molecules and market-approved medicines are poorly soluble in water, resulting in limited drug bioavailability and therapeutic effectiveness. The application of coformers in a multicomponent crystal method is one possible strategy to modulate a drug's solubility. A multicomponent crystal is a solid phase formed when several molecules of different substances crystallize in a crystal lattice with a certain stoichiometric ratio. The goal of this review paper is to comprehensively describe the application of coformers in the formation of multicomponent crystals as solutions for pharmaceutically active ingredients with limited solubility. Owing to their benefits including improved physicochemical profile of pharmaceutically active ingredients, multicomponent crystal methods are predicted to become increasingly prevalent in the development of active drug ingredients in the future.

Energy framework and solubility: a new predictive model in the evaluation of the structure–property relationship of pharmaceutical solid forms

Crystal structures with lower interaction energy tend to present higher aqueous solubility.

Solubility and permeability enhancement of BCS class IV drug ribociclib through cocrystallization

Cocrystallization improves the solubility and permeability of BCS class IV anticancer drug ribociclib as a cocrystal with resorcinol and as a salt hydrate with vanillic acid.

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

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

Rosuvastatin cocrystals: an attempt to modulate physicochemical parameters

Background

The meager physicochemical properties like low solubility and low dissolution rate of rosuvastatin calcium remain as an obstruction for formulation development. In the present work, we explore the evolution of rosuvastatin cocrystal, which may offer the synergetic physico-chemical properties of the drug. Cocrystal crafting depends on two possible intermolecular interactions; heteromeric and the homomeric selection of compounds with complementary functional groups are contemplated as a possible cause of supramolecular synthons in cocrystal formation. Specifically, cocrystals of rosuvastatin with l-asparagine and l-glutamine with molar ratio (1:1) were fabricated by using slow solvent evaporation and slow evaporation techniques. Novel cocrystals of rosuvastatin-asparagine (RSC-C) and rosuvastatin-glutamine (RSC-G) cocrystals obtained by slow solvent evaporation were utilized for preliminary investigation and further scale-up was done by using the solvent evaporation technique.

Results

The novel cocrystals showed a new characteristic of powder X-ray diffraction, thermograms of differential scanning calorimetry, 1H liquid FT-NMR spectra, and scanning electron microscopy. These results signify the establishment of intermolecular interaction within the cocrystals. In both the novel cocrystals, rosuvastatin was determined to be engaged in the hydrogen bond interaction with the complementary functional groups of l-asparagine and l-glutamine. Compared with the pure rosuvastatin, RSC-C and RSC-G cocrystal showed 2.17-fold and 1.60-fold improved solubility respectively. The dissolution test showed that the RSC-C and RSC-G cocrystal exhibited 1.97-fold and 1.94-fold higher dissolution rate than the pure rosuvastatin in pH6.8 phosphate buffer respectively.

Conclusion

Modulation in the chemical environment, improvement in the solubility, and dissolution rate demonstrated the benefit of co-crystallization to improve the physicochemical properties of the drug.

Graphical abstract

Cocrystals of Apixaban with Improved Solubility and Permeability: Formulation, Physicochemical Characterization, Pharmacokinetic Evaluation, and Computational Studies

The objective of the current study was to develop new cocrystals of Apixaban (APX) to improve its solubility and permeability. The molecular interaction between APX and caffeine (CFFN) was further studied by Raman spectroscopy. The results of all eight studied conformers revealed that the synthesized APX-CFFN cocrystals had the highest solubility and permeability. The water solubility and permeability of APX in the cocrystal were simultaneously enhanced as compared with pure APX in the physiological pH environment (pH 6.8 and pH 7.4). The X-ray diffraction analysis revealed that the cocrystal has a component molar ratio of 1:1. This was dominated by a three-dimensional hydrogen bonding supramolecular structure. The in vivo pharmacokinetic (PK) study indicated that the mean area under curve (AUC) of APX from the synthesized cocrystal was enhanced more than three-folds than the pure APX. Tablets of APX and APX-CFFN cocrystals were prepared using direct compression method and evaluated for in vitro dissolution profile in phosphate buffers (pH 6.8 and pH 7.4). Computational investigations with molecular dynamics simulations also supported the formation of stable cocrystals. The drug release of APX from the tablets was considerably increased when compared with the pure APX in both pH conditions and it was found to increase with an increase in media pH. The present investigation represents an alternative approach for optimizing physicochemical and PK properties of Biopharmaceutical Classification System class-III drugs without changing its molecular structure and intrinsic bioactivities.

Enhancing the Physiochemical Properties of Puerarin via L-Proline Co-Crystallization: Synthesis, Characterization, and Dissolution Studies of Two Phases of Pharmaceutical Co-Crystals

Puerarin (PUE) is a Chinese traditional medicine known to enhance glucose uptake into the insulin cells to downregulate the blood glucose levels in the treatment of type II diabetes. Nevertheless, the bioavailability of pristine PUE is limited due to its poor solubility and low intestinal permeability. In this work, we demonstrate that the solubility of PUE can be significantly enhanced via its co-crystallization with L-Proline (PRO). Two crystalline phases, namely, the solvate-free form [PUE][PRO] (I) and the solvated form [PUE]₂[PRO]∙EtOH∙(H₂O)₂ (II) are isolated. These two phases are characterized by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), Fourier-transformed infrared (FT-IR) spectra, nuclear magnetic resonance (NMR), and thermogravimetric analysis in association with differential scanning calorimetry (TGA-DSC). The solubility and dissolution rate of both I and II in water, gastrointestinal tract at pH 1.2, and phosphate buffer at pH 6.8 indicates a nearly doubled increase as compared to the pristine PUE. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay of pristine PUE, I and II against murine colon cancer cell lines CT-26 and human kidney cell lines HEK-293 indicated that neither compound exhibits obvious cytotoxicity after 24 h. This work showcases that the readily available and biocompatible PRO can be a promising adjuvant to enhance the physicochemical properties of PUE toward orally administered drug formulation with improved pharmacokinetics.

Novel Purine Alkaloid Cocrystals with Trimesic and Hemimellitic Acids as Coformers: Synthetic Approach and Supramolecular Analysis

In this work, benzene-1,3,5-tricarboxylic (trimesic acid, TMSA) and benzene-1,2,3-tricarboxylic acid (hemimellitic acid, HMLA) were used as coformers for cocrystal synthesis with chosen purine alkaloids. Theobromine (TBR) forms cocrystals TBR·TMSA and TBR·HMLA with these acids. Theophylline (TPH) forms cocrystals TPH·TMSA and TPH·HMLA, the cocrystal hydrate TPH·TMSA·2H₂O and the salt hydrate (TPH)⁺·(HMLA)^-·2H₂O. Caffeine (CAF) forms the cocrystal CAF·TMSA and the cocrystal hydrate CAF·HMLA·H₂O. The purine alkaloid derivatives were obtained by solution crystallization and by neat or liquid-assisted grinding. The powder X-ray diffraction method was used to confirm the synthesis of the novel substances. All of these solids were structurally characterized, and all synthons formed by purine alkaloids and carboxylic acids were recognized using a single-crystal X-ray diffraction method. The Cambridge Structural Database was used to determine the frequency of occurrence of analyzed supramolecular synthons, which is essential at the crystal structure design stage. Determining the influence of structural causes on the various synthon formations and molecular arrangements in the crystal lattice was possible using structurally similar purine alkaloids and two isomers of benzenetricarboxylic acid. Additionally, UV-vis measurements were made to determine the effect of cocrystallization on purine alkaloid solubility.

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

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

Syntheses and crystal structures of hydrated and anhydrous 1:2 cocrystals of oxyresveratrol and zwitterionic proline

The hydrated and anhydrous 1:2 cocrystals of oxyresveratrol (4-[(E)-2-(3,5-di-hydroxy-phen-yl)ethen-yl]benzene-1,3-diol; OXY; C14H12O4) and proline [(S)-pyrrolidine-2-carb-oxy-lic acid; PRO; C5H9NO2], namely, 4-[(E)-2-(3,5-di-hydroxy-phen-yl)ethen-yl]benzene-1,3-diol bis-[(S)-pyrrolidin-1-ium-2-carboxyl-ate] monohydrate, C14H12O4·2C5H9NO2·H2O, and the anhydrous form, C14H12O4·2C5H9NO2, were obtained by crystallization at different temperatures. Both of them crystallize with ortho-rhom-bic (P212121) symmetry. The structures display N-H⋯O and O-H⋯O hydrogen-bonding inter-actions between PRO and PRO, OXY and OXY, and OXY and PRO. In the hydrated cocrystal, these types of contacts are also observed between the OXY, PRO and water mol-ecules. A combination of these inter-actions leads to a three-dimensional supra-molecular assembly in each case. Hirshfeld surfaces were used to gain further insight into the inter-molecular inter-actions in the packing, including the relative percentage contributions of the significant inter-molecular H⋯H and H⋯O/O⋯H contacts.

Pharmaceutical salts/cocrystals of enoxacin with dicarboxylic acids: Enhancing in vitro antibacterial activity of enoxacin by improving the solubility and permeability

Base on improving the solubility and permeability of enoxacin (EX) to enhance the antibacterial activity in vitro, three new pharmaceutical salts/cocrystals of EX with oxalic acid (EX·0.5(C₂H₂O₄)·2(H₂O)), malonic acid ((HEX)·C₃H₃O₄) and fumaric acid ((HEX)·C₄H₃O₄) have been designed, synthesized and characterized. Comprehensive analysis structure and Hirshfeld surface reveal that the hydrogen bonds/CAHBs formed by the N atom in the piperazine ring from EX molecule with the carboxylic acid group in the coformer could form a stable crystal structure. It is universally acknowledged that improving the solubility of the EX (BCS class II) to make it a BCS class I drug would obtain a Bioequivalence of immunity to the drug trial. The solubilities of three pharmaceutical salts/cocrystals of EX with dicarboxylic acids are consistent with expectation that they are dramatically improved in pure water than pure enoxacin, and the solubility order of three pharmaceutical salts/cocrystals of EX is consistent with coformers solubility. The permeabilities of three pharmaceutical salts/cocrystals of EX are improved compared with the pure enoxacin, and the variation tendency is consistent with the solubilities of three pharmaceutical salts/cocrystals of EX. In addition, the antibacterial activities in vitro of three pharmaceutical salts/cocrystals of EX are improved compared with the corresponding parent compound (EX), which change the order is consistent with the solubility and permeability. Simultaneously, the hygroscopic stabilities of three pharmaceutical salts/cocrystals are surpassing pure EX, and the hygroscopic stability of molecular cocrystal EX-OXA is better than ionic cocrystal EX-MLO and EX-FUM. This implies that preparation of the pharmaceutical salts/cocrystals of EX with oxalic acid, malonic acid and fumaric acid could not only enhance the antibacterial activity of EX, which base on improving the solubility and permeability of EX, but also improve the hygroscopic stability of EX.

The first zwitterionic cocrystal of indomethacin with amino acid showing optimized physicochemical properties as well as accelerated absorption and slowed elimination in vivo

The first zwitterionic cocrystal of indomethacin (INC) with proline (PL) with optimized in vitro/in vivo properties was prepared and characterized.

Identification of a previously unreported co-crystal form of acetazolamide: a combination of multiple experimental and virtual screening methods

In this work, we demonstrate an approach of trying multiple methods in a more comprehensive search for co-crystals of acetazolamide.

Progress on cocrystallization of poorly soluble NME's in the last decade

Cocrystallization of pharmaceuticals has been an exciting field of interest to both academia and industries, demonstrated from its increasing growth rate of publications, patents, and marketed formulations.

A crystalline solid adduct of sulfathiazole–amantadine: the first dual-drug molecular salt containing both antiviral and antibacterial ingredients

The physicochemical properties and bioactivity of a newly synthesized dual-drug molecular salt, sulfathiazole–amantadine, are theoretically and experimentally studied.

Solvates of acotiamide hydrochloride: characterization and phase transformation

Five novel crystals of acotiamide hydrochloride (AH) with solvates dimethyl formide (DMF), dimethyl sulfoxide (DMSO), ethyl acetate (EA) and water (W) [1AH-1W-1DMF, 1AH-1DMSO-I, 1AH-1DMSO-II, 1AH-1W-1DMSO and 2AH-2DMSO-1EA] were characterized using single-crystal X-ray diffraction, powder X-ray diffraction, thermal analysis and Fourier transform infrared spectroscopy. The five crystals can be divided into four distinct structural types based on analysis of their similarities; 1AH-1W-1DMF and 1AH-1W-1DMSO are isostructural. The benzene rings in 1AH-1DMSO-I, 1AH-1DMSO-II and 2AH-2DMSO-1EA can rotate 180°, and the intramolecular hydrogen bond changes from an OH...C=O bond to an NH...OH bond relative to what is seen in 1AH-1W-1DMF and 1AH-1W-1DMSO. Phase transformation experiments show that a humidity-induced phase transformation is closely tied to moisture content.

Drug–drug salts of mefenamic acid\tolfenamic acid and piperazine to improve physicochemical properties for potential veterinary use

Drug–drug salts of mefenamic acid\tolfenamic acid and piperazine were designed to improve the solubility and hygroscopicity, which could possibly extend the drug–drug salt form into veterinary use.