Screening, crystal structures and solubility studies of a series of multidrug salt hydrates and cocrystals of fenamic acids with trimethoprim and sulfamethazine

Pharmaceutical cocrystals: a rising star in drug delivery applications

Pharmaceutical cocrystals, owing to their manifold applications, are acting as bridge between drug discovery and pharmaceutical product development. The ability to scale up pharmaceutical cocrystals through continuous manufacturing approaches offers superior and economic pharmaceutical products. Moreover, cocrystals can be an aid for the nanoparticulate systems to solve the issues related to scale-up and cost. Cocrystals grabbed attention of academic researchers and pharmaceutical scientist due to their potential to target various diseases like cancer. The present review is mainly focussed on the diverse and comprehensive applications of pharmaceutical cocrystals in drug delivery including solubility and dissolution enhancement, improvement of bioavailability of drug, mechanical and flow properties of active pharmaceutical ingredients, controlled/sustained release and colour tuning of API. Besides, phytochemical based cocrystals, multi-drug cocrystals and cocrystals for tumour therapy have been discussed in this review. Additionally, recent progress pertinent to pharmaceutical cocrystals is also included, which may provide future directions to manufacturing and scale-up of cocrystals.

Bifonazole caffeate: The first molecular salt of bifonazole with enhanced biopharmaceutical property based on experiments and quantum chemistry research

In order to make novel breakthroughs in molecular salt studies of BCS class-IV antifungal medication bifonazole (BIF), a salification-driven strategy towards ameliorating attributes and aiding augment efficiency is raised. This strategy fully harnesses structural characters together attributes and benefits of caffeic acid (CAF) to concurrently enhance dissolvability and permeability of BIF by introducing the two ingredients into the identical molecular salt lattice through the salification reaction, which, coupled with the aroused potential activity of CAF significantly amplifies the antifungal efficacy of BIF. Guided by this route, the first BIF-organic molecular salt, BIF-CAF, is directionally designed and synthesized with satisfactorily structural characterizations and integrated theoretical and experimental explorations on the pharmaceutical properties. Single-crystal X-ray diffraction resolving confirms that there is a lipid-water amphiphilic sandwich structure constructed by robust charge-assistant hydrogen bonds in the salt crystal, endowing the molecular salt with the potential to enhance both dissolvability and permeability relative to the parent drug, which is validated by experimental evaluations. Remarkably, the comprehensive DFT-based theoretical investigations covering frontier molecular orbital, molecular electrostatic potential, Hirshfeld surface analysis, reduced density gradient, topology, sphericity and planarity analysis strongly support these observations, thereby allowing some positive relationships between macroscopic properties and microstructures of the molecular salt can be made. Intriguingly, the optimal properties, together with the stimulated activity of CAF markedly augment in vitro antifungal ability of the molecular salt, with magnifying inhibition zones and reducing minimum inhibitory concentrations. These findings fill in the gaps on researches of BIF-organic molecular salt, and adequately exemplify the feasibility and validity by integrating theoretical and experimental approaches to resolve BIF's problems via the salification-driven tactic.

Trimethoprim-Based multicomponent solid Systems: Mechanochemical Screening, characterization and antibacterial activity assessment

In this work, multicomponent trimethoprim-based pharmaceutical solid systems were developed by mechanochemistry, using coformers from the GRAS list and other active pharmaceutical ingredients. The choice of coformers took into account their potential to increase the aqueous solubility/dissolution rate of TMP or its antibacterial activity. All the binary systems were characterized by thermal analysis, powder X-ray diffraction and infrared spectroscopy, and 3 equimolar systems with FTIR pointing to salts, and 4 eutectic mixtures were identified. The intrinsic dissolution rate of TMP in combination with nicotinic acid (a salt) and with paracetamol (eutectic mixture) were 25% and 5% higher than for pure TMP, respectively. For both Gram-positive and -negative strains, the antibacterial activity of TMP with some of the coformers was improved, since the dosage used was lower than the TMP control. A significant increase in antibacterial activity against E. coli was found for the eutectic mixture with curcumin, with the best results being obtained for the eutectic and equimolar mixtures with ciprofloxacin. Combining trimethoprim with coformers offers an interesting alternative to using trimethoprim alone: multicomponent forms with enhanced TMP dissolution rates were identified, as well as combinations showing enhanced antibacterial activity relatively to the pure drug.

Molecular complexes of drug combinations: A review of cocrystals, salts, coamorphous systems and amorphous solid dispersions

As the advancements in the medical technology and healthcare develop through the years, combinational therapy has evolved to be an important treatment modality in many disease settings, including cancer, cardiovascular disease and infectious diseases. In an effort to alleviate "pill burden" and improve patient compliance, fixed dose combinations (FDCs) have been developed to be used as effective therapeutics. Among all FDCs, the category of drug-drug molecular complexes has been proven an efficient methodology in designing and treating diseases, with many drugs being approved. Among all drug-drug molecular complexes, drug-drug cocrystals, salts, coamorphous systems and solid dispersions have been successfully developed and many have been approved by the FDA. In this review, we dwell deeply into the molecular mechanisms behind the different types of drug-drug molecular complexes, including the key functional groups involved in the intermolecular interactions, the applications of each category of molecular complexes, as well as the advantages and challenges thereof. This comprehensive review provides useful insights into the practical design and manufacture of drug-drug molecular complexes and points out the future direction for the development of new advantageous combinational therapies that benefit more patients.

One Step In Situ Co-Crystallization of Dapsone and Polyethylene Glycols during Fluidized Bed Granulation

Several studies have demonstrated the feasibility of in situ co-crystallization in different pharmaceutical processes such as spray drying, hot melt extrusion, and fluidized bed granulation (FBG) to produce co-crystal-in-excipient formulations. However, no previous studies have examined such a one step in situ co-crystallization process for co-crystal formulations where the coformer is a polymer. In the current study, we explored the use of FBG to produce co-crystal granules of dapsone (DAP) and different molecular weight polyethylene glycols (PEGs). Solvent evaporation (SE) was proven to generate DAP-PEGs co-crystals at a particular weight ratio of 55:45 w/w between DAP and PEG, which was subsequently used in FBG, using microcrystalline cellulose and hydroxypropyl methyl cellulose as filler excipient and binder, respectively. FBG could generate co-crystals with higher purity than SE. Granules containing DAP-PEG 400 co-crystal could be prepared without any additional binder. DAP-PEG co-crystal granules produced by FBG demonstrated superior pharmaceutical properties, including flow properties and tableting properties, compared to DAP and DAP-PEG co-crystals prepared by SE. Overall, in situ co-crystallization via FBG can effectively produce API-polymer co-crystals and enhance the pharmaceutical properties.

Differences in Coformer Interactions of the 2,4-Diaminopyrimidines Pyrimethamine and Trimethoprim

The identification and study of supramolecular synthons is a fundamental task in the design of pharmaceutical cocrystals. The malaria drug pyrimethamine (pyr) and the antibiotic trimethoprim (tmp) are both 2,4-diaminopyrimidine derivatives, providing the same C-NH₂/N=C/C-NH₂ and C-NH₂/N=C interaction sites. In this article, we analyze and compare the synthons observed in the crystal structures of tmp and pyr cocrystals and molecular salts with sulfamethazine (smz), α-ketoglutaric acid (keto), oxalic acid (ox), sebacic acid (seb), and azeliac acid (az). We show that the same coformer interacts with different binding sites of the 2,4-diaminopyrimidine ring in the respective tmp and pyr cocrystals or binds at the same site but gives H bonding patterns with different graph set notions. Pyr·smz·CH₃OH is the first crystal structure in which the interaction of the sulfa drug at the C-NH₂/N=C/C-NH₂ site with three parallel NH₂···N, N···NH_sulfonamide, and NH₂···O=S H bonds is observed. The main synthon in (tmp⁺)(keto^-).0.5H₂O and (tmp⁺)₂(ox^2-)·2CH₃OH is the motif of fused R ₂ ¹(6) and R ₁ ²(5) rings instead of the R ₂ ²(8) motif typically observed in tmp⁺ and pyr⁺ carboxylates. Tmp/az is a rare example of cocrystal-salt polymorphism where the two solid-state forms have the same composition, stoichiometry, and main synthon. Theoretical calculations were performed to understand the order of stability, which is tmp·az cocrystal > (tmp⁺)(az^-) salt. Finally, two three-component tmp/sulfa drug/carboxylate cocrystals with a unique ternary synthon are described.

Multicomponent Solids of Niflumic and Mefenamic Acids Based on Acid-Pyridine Synthon

The present study discusses comparative structural features of fourteen multicomponent solids of two non-steroidal anti-inflammatory drugs, Niflumic and Mefenamic acids, with amine and pyridine-based coformers. All the solids were structurally characterized through PXRD, SCXRD, DSC, and the monophasic nature of some of the solids was established through Rietveld refinement. The solid forms include salt, cocrystal, hydrate, and solvate. Except for two, all the solids reported here showed relatively higher solubility compared to the acids. The difference in pKa and similarity in structural features of both the molecules enabled us to study the effect of ΔpKa on crystallization outcome systematically. The structures of all the solids are described through acid-pyridine synthon perspective.

Enhanced phytoremediation of Metal(loid)s via spiked ZVI nanoparticles: An urban clean-up strategy with ornamental plants

The increasing industrialization and urbanization are also triggering environmental pollution, mostly unnoticed, in the case of soil pollution due to uncontrolled contamination by toxic elemental dispersion. The present study focused on this aspect and studied the clean-up of urban soil in a low-cost and eco-friendly way to restrict arsenic (As), lead (Pb) and mercury (Hg) contamination. Four potential ornamental plants, Catharanthus roseus (vinca), Cosmos bipinnatus (cosmos), Gomphrena globose (globosa) and Impatiens balsamina (balsamina) were used along with zero valent iron (ZVI) nanoparticles (Fe NPs) for remediation of the soil spiked with As (70 mg kg-1), Pb (600 mg kg-1) and Hg (15 mg kg-1) in a 60 d pot experiment. All plants were divided into four groups viz. control, spiked, spiked+20 mg kg-1 ZVI NP and spiked+50 mg kg-1 ZVI NP. FTIR and SEM were used for ZVI NP characterization. Soil and plant analyses and elemental assessments were done using ICP-MS, XRF and SEM. Among the four plants, cosmos showed the maximum accumulation of toxic elements (41.24 ± 0.022 mg kg-1 As, 139.15 ± 11.2 mg kg-1 Pb and 15.57 ± 0.27 mg kg-1 Hg) at 60 d. The application of ZVI NP at 20 mg kg-1 dosage was found to further augment plants' potential for metal(loid)s accumulation without negatively hampering their growth. Cosmos were observed to reduce soil As from 81.35 ± 1.34 mg kg-1 to 28.16 ± 1.38 mg kg-1 (65.38%), Pb from 1132.47 ± 4.66 to 516.09 ± 3.15 mg kg-1 (54.42%) and Hg from 17.35 ± 0.88 to 6.65 ± 0.4 mg kg-1 (61.67%) at 60 d in spiked + 20 mg kg-1 ZVI NP treatment. Balsamina was the most sensitive plant and showed the least metal(loid)s accumulation. In conclusion, three of these plants are potent enough to use together for a better and enhanced removal of toxic elements from the contaminated soil with cosmos to be the best amongst these in urban areas.

Multicomponent Crystal of Trimethoprim and Citric Acid: Solid State Characterization and Dissolution Rate Studies

BACKGROUND: Trimethoprim is a broad spectrum antimicrobial agent with low solubility in water which causes low bioavailability in systemic circulation. AIM: The purpose of this study was to prepare multicomponent crystals of trimethoprim and citric acid to increase the solubility and dissolution rate of trimethoprim. MATERIALS AND METHODS: Multicomponent crystals were prepared by solvent evaporation method. Characterizations of multicomponent crystalline solid phase properties were carried out by powder X-ray diffraction (PXRD) analysis, differential scanning calorimetry (DSC), FT-IR spectroscopy, scanning electron microscopy (SEM). Solubility and dissolution rate tests were carried out in aqueous medium. RESULTS: The PXRD characterization results showed a new X-ray diffraction pattern in the multicomponent crystal phase. DSC analysis showed the formation of a new endothermic peak. This indicates the formation of a multicomponent crystal phase between trimethoprim and citric acid. The results of the SEM analysis indicate the formation of a new crystal habit. Solubility of multi-component crystal phase of trimethoprim increased 7 times compared to intact trimethoprim. The dissolution of trimethoprim and multicomponent crystals in 0.1 N HCl medium at 60 minutes was 56.36% and 95.57% and CO2-free distilled water medium was 43.03% and 88.26%, respectively. CONCLUSIONS: From the results of the study, it can be concluded that the multicomponent phase of trimethoprim crystals with citric acid successfully increase the solubility and dissolution rate of trimethoprim significantly.

Cocrystallization-driven self-assembly with vanillic acid offers a new opportunity for surmounting fast and excessive absorption issues of antifungal drug 5-fluorocytosine: a combined theoretical and experimental research

The cocrystal of 5-fluorocytosine (FCY) with vanillic acid (VAA) was assembled via a cocrystallization technique, giving a novel understanding for conquering the dose-limited hepatotoxicity caused by the rapid and almost complete absorption of FCY.

The solid state of anti-inflammatory morniflumate diniflumate: A cocrystalline salt

Morniflumate diniflumate, a molecular compound involving niflumic acid and its β-morpholino ethyl ester (morniflumate) in the mole ratio 2:1, is found to crystallize in a triclinic P - 1 space group with a unit-cell volume of 2203.4(5) ų. It is a cocrystal between a morniflumate⁺ niflumate^- salt and a neutral niflumic acid molecule. The co-crystalline salt forms endothermically with a positive excess volume and it melts incongruently at 382.3(8) K. Differential scanning calorimetry executed at heating rates above 20 K⋅min^-1, leads to congruent melting at 387.8(9)K with an enthalpy change of Δ_fusH = 80(2) J g^-1. The rare occurrence that incongruent and congruent melting can be observed for the same cocrystal may be due to the conformational versatility of the niflumic acid molecule and its slow conversion between the different conformations due to weak intramolecular hydrogen bonding.

Novel Polymorphic Cocrystals of the Non-Steroidal Anti-Inflammatory Drug Niflumic Acid: Expanding the Pharmaceutical Landscape

Any time the pharmaceutical industry develops a new drug, potential polymorphic events must be thoroughly described, because in a crystalline pharmaceutical solid, different arrangements of the same active pharmaceutical ingredient can yield to very different physicochemical properties that might be crucial for its efficacy, such as dissolution, solubility, or stability. Polymorphism in cocrystal formulation cannot be neglected, either. In this work, two different cocrystal polymorphs of the non-steroidal anti-inflammatory drug niflumic acid and caffeine are reported. They have been synthesized by mechanochemical methods and thoroughly characterized in solid-state by powder and single crystal X-ray diffraction respectively, as well as other techniques such as thermal analyses, infrared spectroscopy and computational methods. Both theoretical and experimental results are in agreement, confirming a conformational polymorphism. The polymorph NIF-CAF Form I exhibits improved solubility and dissolution rate compared to NIF-CAF Form II, although Form II is significantly more stable than Form I. The conditions needed to obtain these polymorphs and their transition have been carefully characterized, revealing an intricate system.

Dihydrofolate Reductase Inhibitors: The Pharmacophore as a Guide for Co-Crystal Screening

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons.

Challenges and Progress in Nonsteroidal Anti-Inflammatory Drugs Co-Crystal Development

Co-crystal innovation is an opportunity in drug development for both scientists and industry. In line with the “green pharmacy” concept for obtaining safer methods and advanced pharmaceutical products, co-crystallization is one of the most promising approaches to find novel patent drugs, including non-steroidal anti-inflammatory drugs (NSAID). This kind of multi-component system improves previously poor physicochemical and mechanical properties through non-covalent interactions. Practically, there are many challenges to find commercially viable co-crystal drugs. The difficulty in selecting co-formers becomes the primary problem, followed by unexpected results, such as decreased solubility and dissolution, spring and parachute effect, microenvironment pH effects, changes in instability, and polymorphisms, which can occur during the co-crystal development. However, over time, NSAID co-crystals have been continuously updated regarding co-formers selection and methods development.

Mechanochemistry: A Green Approach in the Preparation of Pharmaceutical Cocrystals

Mechanochemistry is considered an alternative attractive greener approach to prepare diverse molecular compounds and has become an important synthetic tool in different fields (e.g., physics, chemistry, and material science) since is considered an ecofriendly procedure that can be carried out under solvent free conditions or in the presence of minimal quantities of solvent (catalytic amounts). Being able to substitute, in many cases, classical solution reactions often requiring significant amounts of solvents. These sustainable methods have had an enormous impact on a great variety of chemistry fields, including catalysis, organic synthesis, metal complexes formation, preparation of multicomponent pharmaceutical solid forms, etc. In this sense, we are interested in highlighting the advantages of mechanochemical methods on the obtaining of pharmaceutical cocrystals. Hence, in this review, we describe and discuss the relevance of mechanochemical procedures in the formation of multicomponent solid forms focusing on pharmaceutical cocrystals. Additionally, at the end of this paper, we collect a chronological survey of the most representative scientific papers reporting the mechanochemical synthesis of cocrystals.

Study on Co-Crystallization of LCZ696 Using In Situ ATR-FTIR and Imaging

In situ ATR-FTIR spectroscopy and imaging and image analysis were applied to the study of the multicomponent co-crystallization process involving S-valsartan and sacubitril in which LCZ696 crystals were formed. LCZ696 is a combination drug for use in heart failure that was approved by the FDA in 2015 following development by Novartis Pharmaceuticals. Though much work was reported on LCZ696 about its pharmacokinetic and pharmacodynamic effects in the evaluation and clinical testing, less attention was paid to study on the co-crystallization process. LCZ696 crystals have shown difficulties in filtration mainly due to the small particle size. In this work, LCZ696 crystals were prepared successfully by S-valsartan and sacubitril, and characterized by SEM, XRPD, TG-DSC and ATR-FTIR. ATR-FTIR and imaging and image analysis were used to monitoring solution concentration and investigating the co-crystallization mechanism. It revealed that the nucleation process was very slow compared with the transformation process, which is indication that the co-crystallization was controlled by nucleation. LCZ696 crystals are composed of very thin hexagonal plates, which seems indicating that LCZ696 crystals grow mainly in two size dimensions. Stirrer speed and crystal seeds were found to have noticeable effect on the induction time, transformation time and crystal size distribution. The Johnson-Mehl-Avrami equation was found to be able to describe the co-crystallization process.

Cocrystallization: Cutting Edge Tool for Physicochemical Modulation of Active Pharmaceutical Ingredients

Cocrystallization is a widely accepted and clinically relevant technique that has prospered very well over the past decades to potentially modify the physicochemical properties of existing active pharmaceutic ingredients (APIs) without compromising their therapeutic benefits. Over time, it has become an integral part of the pre-formulation stage of drug development because of its ability to yield cocrystals with improved properties in a way that other traditional methods cannot easily achieve. Cocrystals are solid crystalline materials composed of two or more than two molecules which are non-covalently bonded in the same crystal lattice. Due to the continuous efforts of pharmaceutical scientists and crystal engineers, today cocrystals have emerged as a cutting edge tool to modulate poor physicochemical properties of APIs such as solubility, permeability, bioavailability, improving poor mechanical properties and taste masking. The success of cocrystals can be traced back by looking at the number of products that are getting regulatory approval. At present, many cocrystals have obtained regulatory approval and they successfully made into the market place followed by a fair number of cocrystals that are currently in the clinical phases. Considering all these facts about cocrystals, the formulation scientists have been inspired to undertake more relevant research to extract out maximum benefits. Here in this review cocrystallization technique will be discussed in detail with respect to its background, different synthesis approaches, synthesis mechanism, application and improvements in drug delivery systems and its regulatory perspective.

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.

Mechanochemical cocrystallization to improve the physicochemical properties of chlorzoxazone

Cocrystals of chlorzoxazone prepared by mechanochemical cocrystallization with picolinic acid to improve the physicochemical properties.