Indomethacin co-crystals and their parent mixtures: does the intestinal barrier recognize them differently?

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.

Cocrystallization of 5-fluorouracil with gallic acid: A novel 5-fluorouracil cocrystal displaying synergistic anti-tumor activity both in oral and intraperitoneal injection administration

Gallic acid (GA) is a naturally occurring polyphenolic compound exhibiting anti-tumor activity. To clarify the capability of GA in optimizing the in vitro/in vivo properties of the first line anti-tumor drug 5-fluorouracil (5-FU) and achieve synergistically enhanced anti-tumor activity, a novel cocrystal hydrate of 5-FU-GA-H₂O was successfully screened and characterized based on various spectroscopic and experimental analysis including Fourier transform infrared spectroscopy (FT-IR), Raman spectra (Raman), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric (TG) and scanning electric microscope (SEM) techniques. The results suggested the existence of hydrogen bonding interactions between C=O group of 5-FU and O-H group of GA. Although the dissolution rate and solubility of 5-FU-GA-H₂O cocrystal were slowed and lowered compared with that of 5-FU, respectively, the membrane permeability was enhanced for cocrystal compared with that of intact 5-FU and physical mixture (PM) of 5-FU and GA. For the cocrystal, the cumulative amount per unit area of permeated 5-FU in the first 10 h was 2.56 and 9.97 times of that of pure 5-FU and PM, respectively, in the case that transmembrane behavior of 5-FU depended on the type of solution from which the powder was dissolved. Meanwhile, improvement on oral bioavailability by co-crystallization was observed; AUC_0-t of cocrystal was 2.78-fold higher than that of 5-FU. Furthermore, the cocrystal displayed a superior cytotoxic activity on 4T1 mouse breast cancer cells compared with pure 5-FU and even the PM. It was confirmed that the cocrystal solution induced higher autophagic flux than those of 5-FU and PM in 4T1 cell, suggesting that autophagy rather than apoptosis mainly mediated cell death. The obvious difference of tumor inhibition activity between PM and cocrystal in intraperitoneal injection administration indicated that some of the interactions formed in the solid cocrystal could retain in solution in some way. Benefiting from synergistic cytotoxicity, drug efficacy in vivo was enhanced through injection administration of solution from which cocrystal was dissolved.

Preparation, characterization, and pharmacokinetics of rivaroxaban cocrystals with enhanced in vitro and in vivo properties in beagle dogs

Rivaroxaban (RIV) is a direct Factor Xa inhibitor anticoagulant, but the oral bioavailability of RIV is estimated to be only 60% due to its poor solubility. The aim of the present study was to improve the solubility and bioavailability of RIV. Five cocrystals—p-hydroxybenzoic acid (HBA), 2,4-dihydroxybenzoic acid (DBA), nicotinamide (NA), isonicotinamide (IA), and succinic acid (SA)—were used as cofomers and were successfully obtained and characterized by powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectra. RIV-DBA and RIV-HBA cocrystals showed obvious improvements in solubility, dissolution (under sink conditions), and intrinsic dissolution rates versus RIV. Moreover, the dissolution of RIV-HBA, RIV-DBA, and RIV-SA cocrystals under non-sink conditions showed obvious “spring and parachute” patterns. The in vitro permeability levels in a Caco-2 cell model of RIV-DBA and RIV-IA cocrystals were significantly improved versus RIV. Pharmacokinetic studies in beagle dogs showed that RIV-DBA and RIV-HBA cocrystals had higher bioavailability than RIV. The enhancements in solubility and bioavailability indicate the potential of RIV cocrystals as a better candidate for the treatment of thrombosis versus RIV.

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.

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.

Cocrystals Based on 4,4’-bipyridine: Influence of Crystal Packing on Melting Point

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4’-bipyridine (4,4’-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4’-bipy molar ratios, (HPip)(4,4’-bipy) (1) and (HCinn)2(4,4’-bipy) (2). The melting point (m.p.) of these cocrystals have been measured and a remarkable difference (ΔT ≈ 78 °C) between them was observed. Moreover, the two cocrystals have been characterized by powder X-ray diffraction (PXRD), elemental analysis (EA), FTIR-ATR, 1H NMR spectroscopies, and single-crystal X-ray diffraction. The study of their structural packings via Hirshfeld surface analysis and energy frameworks revealed the important contribution of the π···π and C-H···π interactions to the formation of different structural packing motifs, this being the main reason for the difference of m.p. between them. Moreover, it has been observed that 1 and 2 presented the same packing motifs as the crystal structure of their corresponding carboxylic acids, but 1 and 2 showed lower m.p. than those of the carboxylic acids, which could be related to the lower strength of the acid-pyridine heterosynthons respect to the acid-acid homosynthons in the crystal structures.

Solubility improvement of curcumin with amino acids

Eutectic, co-amorphous, cocrystal, and physical mixtures of curcumin with basic amino acids are prepared and characterized by PXRD, DSC, NMR, FT-IR, and SEM; solubility and dissolution improvement achieved in 40% ethanol–water system.

Sacubitril-valsartan cocrystal revisited: role of polymer excipients in the formulation

Objectives: This study investigated the impact of polymer excipients on a typical cocrystal for sacubitril (SAC) and valsartan (VAL), aiming to guide optional formulation design and maximize oral bioavailability.Methods: Poly vinyl pyrrolidone (PVP) and hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) were selected. The dissolution/permeation system was used to predict both the kinetics of drug supersaturation and the simple permeation. The intermolecular interaction was analyzed by ¹H NMR spectroscopy and molecular dynamics simulation. Pharmacokinetic study was performed to assess the impact of polymer excipients in vivo.Results: Our study found that unappreciated excipients in the formulation, especially some polymers, might compete with the intermolecular hydrogen bonding among the cocrystals components and provide unexpected affinity, and thus leverage the therapeutic benefits. HPMC as a coating excipient used in the Entresto® tablet hampered the supersaturation of API, which led to the poor oral absorption of cocrystals. Conversely, PVP appeared to promote and maintain drug supersaturation, resulting in improved bioavailability of API.Conclusion: In conclusion, understanding the interplay between the cocrystal components and polymers is the key to optimizing the excipients to maximize the performance of cocrystal based oral drug formulation.

Interactions between dipfluzine-based complexes and cytochrome P450 enzymes: Information on salt, cocrystal, and salt cocrystal complexes

In the new drugs, greater than 90 % of active pharmaceutical ingredients (APIs) or marketed drugs have poor solubility and bioavailability, which restrict the development of pharmaceutical preparations. The use of crystalline molecular complexes (CMCs) involving API and biocompatible precursors to improve solubility has become a shortcut for new drug development. Most of the new drugs registered in CMC form are from postmarketing drugs, and the interaction between these drugs and cytochrome P-450 (CYP) enzymes is well documented. However, it is unclear whether the interactions between CMCs of postmarketing drugs and CYP enzymes should be re-evaluated. To clarify this problem, three dipfluzine (Dip)-based CMCs, including Dip-benzoic acid (BA) cocrystal, Dip-2-hydroxybenzoate (2HB) salt and Dip-4-hydroxybenzoate (4HB) salt-cocrystal, were chosen to investigate the interaction with CYP enzymes. Metabolites of Dip-based CMCs and cocktail probe drugs were measured via LC-MS/MS in the incubation reaction system comprising recombinant CYP enzymes (rCYPs) and human liver microsomes. Dip-based CMCs not only alter Dip-mediated inhibition or activation of CYP enzymes but also change the degree to which rCYPs are involved in Dip metabolism. Specifically, the inhibitory effects of Dip and Dip-HCl were increased compared with Dip-BA and Dip-2HB for CYP1A2; Dip-BA, Dip-2HB and Dip-4HB for CYP3A4; and Dip-BA for CYP2E1. The inhibitory effects of Dip and Dip-HCl were reduced compared with Dip-2HB and Dip-4HB for CYP2C19 and Dip-4HB for CYP2E1. The effects of the alterations of Dip CMCs on the interaction between Dip and CYP enzymes are not attributed to a simple superposition of Dip and the respective precursor and may be due to the presence of interaction forces between Dip and precursor molecules. These results are the first to provide preliminary experimental evidence that CMCs change the interaction between API and CYP enzymes. Moreover, these results further suggest the importance of re-evaluating interactions with CYP enzymes when CMC strategies are used to design new drugs and even for CMCs of postmarketing drugs with known metabolic characteristics.

Characterizations and Assays of α-Glucosidase Inhibition Activity on Gallic Acid Cocrystals: Can the Cocrystals be Defined as a New Chemical Entity During Binding with the α-Glucosidase?

Cocrystallization with co-former (CCF) has proved to be a powerful approach to improve the solubility and even bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). However, it is still uncertain whether a cocrystal would exert the pharmacological activity in the form of a new chemical entity, an API-CCF supramolecule. In the present study, gallic acid (GA)-glutaric acid and GA-succinimide cocrystals were screened. The solubility, dissolution rate and oral bioavailability of the two cocrystals were evaluated. As expected, AUCs of GA-glutaric acid and GA-succinimide cocrystals were 1.86-fold and 2.60-fold higher than that of single GA, respectively. Moreover, experimental evaluations on α-glucosidase inhibition activity in vitro and theoretical simulations were used to detect whether the two cocrystals would be recognized as a new chemical entity during binding with α-glucosidase, a target protein in hypoglycemic mechanisms. The enzyme activity evaluation results showed that both GA and glutaric acid displayed α-glucosidase inhibition activity, and GA-glutaric acid cocrystals showed strengthened α-glucosidase inhibition activity at a moderate concentration, which is attributed to synergism of the two components. Molecular docking displayed that the GA-glutaric acid complex deeply entered the active cavity of the α-glucosidase in the form of a supramolecule, which made the guest-enzyme binding configuration more stable. For the GA and succinimide system, succinimide showed no enzyme inhibition activity, however, the GA-succinimide complex presented slightly higher α-glucosidase inhibition activity than that of GA. Molecular docking simulation indicated that the guest molecules entering the active cavity of the α-glucosidase were free GA and succinimide, not the GA-succinimide supramolecule.

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.

Dissolution Advantage of Nitazoxanide Cocrystals in the Presence of Cellulosic Polymers

The effect of hydroxypropyl methylcellulose (HPMC) and methylcellulose (Methocel^® 60 HG) on the dissolution behavior of two cocrystals derived from nitazoxanide (NTZ), viz., nitazoxanide-glutaric acid (NTZ-GLU, 1:1) and nitazoxanide-succinic acid (NTZ-SUC, 2:1), was explored. Powder dissolution experiments under non-sink conditions showed similar dissolution profiles for the cocrystals and pure NTZ. However, pre-dissolved cellulosic polymer in the phosphate dissolution medium (pH 7.5) modified the dissolution profile of NTZ when starting from the cocrystals, achieving transient drug supersaturation. Subsequent dissolution studies under sink conditions of polymer-based pharmaceutical powder formulations with NTZ-SUC cocrystals gave a significant improvement of the apparent solubility of NTZ when compared with analogous formulations of pure NTZ and the physical mixture of NTZ and SUC. Scanning electron microscopy and powder X-ray diffraction analysis of samples recovered after the powder dissolution studies showed that the cocrystals undergo fast dissolution, drug supersaturation and precipitation both in the absence and presence of polymer, suggesting that the solubilization enhancement is due to polymer-induced delay of nucleation and crystal growth of the less soluble NTZ form. The study demonstrates that the incorporation of an appropriate excipient in adequate concentration can be a key factor for inducing and maintaining the solubilization of poorly soluble drugs starting from co-crystallized solid forms. In such a way, cocrystals can be suitable for the development of solid dosage forms with improved bioavailability and efficacy in the treatment of important parasitic and viral diseases, among others.

In Vitro and In Vivo Evaluation of Core-Shell Mesoporous Silica as a Promising Water-Insoluble Drug Delivery System: Improving the Dissolution Rate and Bioavailability of Celecoxib With Needle-Like Crystallinity

The objective of our study was to prepare mesoporous silica nanoparticles with a core-shell structure (CSMSNs) and improve the dissolution and bioavailability of celecoxib (Cxb), a water-insoluble drug, by changing its needle-like crystal form. CSMSNs are prepared by a core-shell segmentation self-assembly method. The S_BET and V_t of CSMSNs were 890.65 m²/g and 1.23 cm³/g, respectively. Cxb was incorporated into CSMSNs by the solvent evaporation method. The gastrointestinal irritancy of the CSMSNs was evaluated by a gastric mucosa irritation test. In vitro dissolution and in vivo pharmacokinetic tests were carried out to study the improvement in the dissolution behavior and oral bioavailability of Cxb. In conclusion, gastric mucosa irritation study indicated the good biocompatibility of CSMSNs. The cumulative dissolution of CSMSNs-Cxb is 86.2% within 60 min in SIF solution, which may be ascribed to the crystal form change caused by control of the nanochannel for CSMSNs. Moreover, CSMSNs could enhance the 9.9-fold AUC of Cxb. The cumulative dissolution and bioavailability of Cxb were both significantly enhanced by CSMSNs. CSMSNs with a core-shell structure are suitable as a carrier for a poorly water-soluble drug (Cxb).

Investigating Permeation Behavior of Flufenamic Acid Cocrystals Using a Dissolution and Permeation System

The dissolution and permeation of the cocrystals, flufenamic acid-nicotinamide (FFA-NIC) and flufenamic acid-theophylline (FFA-TP), have been investigated in the presence of two polymers, polyvinylpyrrolidone (PVP) and copolymer of vinylpyrrolidone/vinyl acetate (PVP-VA), using a dissolution/permeation (D/P) system. It showed that the types and concentrations of the polymers and their interactions with the coformers had significant effects on the dissolution and permeation of the FFA cocrystals. The role of PVP as a stabilizing agent was not altered in spite of its interaction with the coformer of NIC or TP, which was supported by the proportional flux rate of FFA to the dissolution performance parameter (DPP). With an appropriate PVP concentration, the maximal flux rate of FFA could be obtained for a given FFA cocrystal. The situation was complicated in the presence of PVP-VA. The role of PVP-VA could change because of its association with the coformers, i.e., from a stabilizing agent to a solubilization agent. In addition, PVP-VA reduced the flux rate of FFA, in contrast to its DPP for FFA cocrystals. Finally, ¹H NMR provided evidence regarding the molecular interactions between FFA, coformers, and polymers at the atomic level and gave insight into the mechanism underlying the supersaturated solution and subsequent permeation behavior of the cocrystals.

Hydrogen bonding in hydroxypyridium salts

The crystal structures of 6-methyl-2-ethyl-3-hydroxypyridiniun nitrate (C8H12NO)NO3 (I) and fumarate (C8H12NO)2C4H2O4 (II) were solved and refined from X-ray single crystal diffraction data (CuKα, (I) a=4.6477(2), b=14.5906(9), c=14.5551(8) Å, β=99.100(4)°, space group P21 /c, Z=4, Rp /Rwp =0.033/0.047; (II) a=8.8293(3), b=13.4268(5), c=8.3893(3) Å, β=96.303(3)°, space group P21/c, Z=2, Rp /Rwp= 0.034/0.049). Both structures are built of infinite chains along ac diagonal of the unit cells formed by hydrogen bonding between the hydroxypyridium cation and the corresponding anion. Each fumarate anion is linked to four hydroxypyridium cations while nitrate anion is connected with two hydroxypyridium cations only leaving one oxygen atom in the nitrogen group isolated.

Cocrystallization as a novel approach to enhance the transdermal administration of meloxicam

Despite its large effectiveness, the long-term oral administration of high doses of meloxicam (MLX) may lead to gastrointestinal events such as abdominal pain, diarrhea, dyspepsia, ulceration, hemorrhage, and gastrointestinal perforation. Moreover, the pH-dependent solubility of MLX makes the development of new oral formulations even more challenging. As an alternative to overcome these limitations, the transdermal delivery of this drug has been purposed. Although various physical and chemical approaches to enhance the absorption of MLX may be found in literature, the use of cocrystallization has not been reported so far. Cutaneous permeation of MLX and 1:1 meloxicam-salicylic acid cocrystal (MLX-SLC) were evaluated using Franz diffusion cells. Cocrystal was suspended in an aqueous solution and in a gel to evaluate the vehicle effect on permeation parameters. In aqueous medium, the cocrystallization showed to enhance the drug permeation coefficient from 1.38 to 2.15 × 10^-3 cm/h. MLX-SLC generated supersaturation with respect to the drug during dissolution studies simulating the conditions in the Franz cell donor chamber. This greater amount of free drug in the solution could contribute to explain the higher transdermal absorption and shorter lag time of this system. In addition, the acidic coformer ionization led to a pH reduction from 7.4 to 5.8, which, in turn, provided an increase in the unionized species of the drug, enhancing its permeation rate. The gel containing cocrystals reduced MLX permeation rate significantly (P = 0.42 × 10^-3 cm/h), which was attributed to its higher viscosity.

Recent advances in improving oral drug bioavailability by cocrystals

Introduction: Oral drug delivery is the most favored route of drug administration. However, poor oral bioavailability is one of the leading reasons for insufficient clinical efficacy. Improving oral absorption of drugs with low water solubility and/or low intestinal membrane permeability is an active field of research. Cocrystallization of drugs with appropriate coformers is a promising approach for enhancing oral bioavailability.

Methods: In the present review, we have focused on recent advances that have been made in improving oral absorption through cocrystallization. The covered areas include supersaturation and its importance on oral absorption of cocrystals, permeability of cocrystals through membranes, drug-coformer pharmacokinetic (PK) interactions, conducting in vivo-in vitro correlations for cocrystals. Additionally, a discussion has been made on the integration of nanocrystal technology with supramolecular design. Marketed cocrystal products and PK studies in human subjects are also reported.

Results: Considering supersaturation and consequent precipitation properties is necessary when evaluating dissolution and bioavailability of cocrystals. Appropriate excipients should be included to control precipitation kinetics and to capture solubility advantage of cocrystals. Beside to solubility, cocrystals may modify membrane permeability of drugs. Therefore, cocrystals can find applications in improving oral bioavailability of poorly permeable drugs. It has been shown that cocrystals may interrupt cellular integrity of cellular monolayers which can raise toxicity concerns. Some of coformers may interact with intestinal absorption of drugs through changing intestinal blood flow, metabolism and inhibiting efflux pumps. Therefore, caution should be taken into account when conducting bioavailability studies. Nanosized cocrystals have shown a high potential towards improving absorption of poorly soluble drugs.

Conclusions: Cocrystals have found their way from the proof-of-principle stage to the clinic. Up to now, at least two cocrystal products have gained approval from regulatory bodies. However, there are remaining challenges on safety, predicting in vivo behavior and revealing real potential of cocrystals in the human.

Brain targeting of resveratrol by nasal administration of chitosan-coated lipid microparticles

Lipid microparticles (LMs) uncoated or coated with chitosan and containing the neuroprotective polyphenol resveratrol were developed for its targeting to the brain via nasal administration. The lipid microparticles loaded with resveratrol (LMs-Res) were produced by melt emulsification, using stearic acid as lipid material and phosphatidylcholine as the surfactant. The chitosan coated particles LMs-Res-Ch (1.75% w/v chitosan solution) and LMs-Res-Ch-plus (8.75% w/v chitosan solution) were prepared by adding a chitosan solution to the formed particles. The mean diameter of the particles were 68.5 ± 3.1 μm, 76.3 ± 5.2 μm and 84.5 ± 8.1 μm for LMs-Res, LMs-Res-Ch and LMs-Res-Ch-plus respectively, suitable for nasal delivery. Chitosan coating changed the particle surface charge from a negative zeta potential value (-12.7 ± 2.1 mV) for the uncoated particles to a higher positive values respectively, 24.0 ± 4.7 and 44.6 ± 3.1 mV for the chitosan coated LM-Res-Ch and LM-Res-Ch-plus. Permeation studies across human NCM460 cell monolayers demonstrated that their transepithelial electrical resistance (TEER) values were not modified in the presence of free resveratrol, unloaded LMs, loaded LMs-Res or LMs-Res-Ch. On the other hand, the TEER values decreased from 150 ± 7 to 41 ± 3 Ω cm² in the presence of LMs-Res-Ch-plus, which corresponded to a significant increase in the apparent permeability (P_app) of resveratrol from 518 ± 8 × 10^-4 cm/min to 750 ± 98 × 10^-4 cm/min. In vivo studies demonstrated that no resveratrol was detected in the rat cerebrospinal fluid (CSF) after an intravenous infusion of the polyphenol. Conversely, the nasal delivery of resveratrol in a chitosan suspension or encapsulated in uncoated LMs-Res dispersed in water achieved the uptake of resveratrol in the CSF with C_max after 60 min of 1.30 ± 0.30 μg/ml and 0.79 ± 0.15 μg/ml, respectively. However, a dramatic increase in the levels of resveratrol reaching the CSF was attained by the administration of an aqueous suspension of LMs-Res-Ch-plus with a C_max after 60 min of 9.7 ± 1.9 μg/ml. This marked increase in the CSF bioavailability was achieved without any distribution in the systemic circulation, demonstrating a direct and specific nose to brain delivery.

Geraniol Pharmacokinetics, Bioavailability and Its Multiple Effects on the Liver Antioxidant and Xenobiotic-Metabolizing Enzymes

Geraniol is a natural monoterpene showing anti-inflammatory, antioxidant, neuroprotective and anticancer effects. No pharmacokinetic and bioavailability data on geraniol are currently available. We therefore performed a systematic study to identify the permeation properties of geraniol across intestinal cells, and its pharmacokinetics and bioavailability after intravenous and oral administration to rats. In addition, we systematically investigated the potential hepatotoxic effects of high doses of geraniol on hepatic phase I, phase II and antioxidant enzymatic activities and undertook a hematochemical analysis on mice. Permeation studies performed via HPLC evidenced geraniol permeability coefficients across an in vitro model of the human intestinal wall for apical to basolateral and basolateral to apical transport of 13.10 ± 2.3 × 10^-3 and 2.1 ± 0.1⋅× 10^-3 cm/min, respectively. After intravenous administration of geraniol to rats (50 mg/kg), its concentration in whole blood (detected via HPLC) decreased following an apparent pseudo-first order kinetics with a half-life of 12.5 ± 1.5 min. The absolute bioavailability values of oral formulations (50 mg/kg) of emulsified geraniol or fiber-adsorbed geraniol were 92 and 16%, respectively. Following emulsified oral administration, geraniol amounts in the cerebrospinal fluid of rats ranged between 0.72 ± 0.08 μg/mL and 2.6 ± 0.2 μg/mL within 60 min. Mice treated with 120 mg/kg of geraniol for 4 weeks showed increased anti-oxidative defenses with no signs of liver toxicity. CYP450 enzyme activities appeared only slightly affected by the high dosage of geraniol.

Sulfaguanidine cocrystals: Synthesis, structural characterization and their antibacterial and hemolytic analysis

Sulfaguanidine (SG), belongs to the class of sulfonamide drug used as an effective antibiotic. In the present work, using crystal engineering approach two novel cocrystals of SG were synthesized (SG-TBA and SG-PT) with thiobarbutaric acid (TBA) and 1,10-phenanthroline (PT), characterized by solid state techniques viz., powder X-ray diffraction (PXRD), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and the crystal structures were determined by single crystal X-ray diffraction studies. A comparative antibacterial activity and hemolytic potential was done on SG drug, coformers and their cocrystals. The tested cocrystals formulations showed almost two fold higher antibacterial activity against the tested strains of bacteria Gram-positive bacteria (S. mutans and E. faecalis) and Gram-negative bacteria (E. coli, K. pneumonia and E. clocae) over SG alone and their coformers. Cocrystal SG-TBA showed better antibacterial activity and reduced hemolysis, thereby, reduced cytotoxicity than SG-PT.

New pharmaceutical salts containing pyridoxine

Two mixed crystals were obtained by crystallizing the active pharmaceutical ingredient pyridoxine [systematic name: 4,5-bis(hydroxymethyl)-2-methylpyridin-3-ol, PN] with (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoic acid (ferulic acid) and 4-hydroxy-3,5-dimethoxybenzoic acid (syringic acid). PN and the coformers crystallize in the form of pharmaceutical salts in a 1:1 stoichiometric ratio, namely 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridin-1-ium (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoate, C₈H₁₂NO₃⁺·C₉H₉O₅^-, and 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridin-1-ium 4-hydroxy-3,5-dimethoxybenzoate monohydrate, C₈H₁₂NO₃⁺·C₁₀H₁₁O₅^-·H₂O, the proton exchange between PN and the acidic partner being supported by the differences of the pK_a values of the two components and by the C-O bond lengths of the carboxylate groups. Besides complex hydrogen-bonding networks, π-π interactions between aromatic moieties have been found to be important for the packing architecture in both crystals. Hirshfeld surface analysis was used to explore the intermolecular interactions in detail and compare them with the interactions found in similar pyridoxine/carboxylic acid salts.

Can pharmaceutical co-crystals provide an opportunity to modify the biological properties of drugs?

Poorly soluble and/or permeable molecules jeopardize the discovery and development of innovative medicines. Pharmaceutical co-crystals, formed by an active pharmaceutical substance (API) and a co-crystal former, can show enhanced dissolution and permeation values compared with those of the parent crystalline pure phases. It is currently assumed that co-crystallization with pharmaceutical excipients does not affect the pharmacological activity of an API or, indeed, might even improve physical properties such as solubility and permeability. However, as we highlight here, the biological behavior of co-crystals can differ drastically with respect to that of their parent physical mixtures.

A novel hybrid drug between two potent anti-tubulin agents as a potential prolonged anticancer approach

We report the design, synthesis and biological characterisation of a novel hybrid drug by conjugation of two tubulin inhibitors, a hemiasterlin derivative A (H-Mpa-Tle-Aha-OH), obtained by condensation of three non-natural amino acids, and cis-3,4',5-trimethoxy-3'aminostilbene (B). As we have previously demonstrated synergy between A and B, we used a monocarbonyl derivative of triethylene glycol as linker (L) to synthesise compounds A-L and A-L-B; via HPLC we analysed the release of its potential hydrolysis products A, A-L, B and B-L in physiological fluids: the hybrid A-L-B undergo hydrolysis in rat whole blood of the ester bond between A and L (half-life=118.2±9.5min) but not the carbamate bond between B and L; the hydrolysis product B-L was further hydrolyzed, but with a slower rate (half-life=288±12min). The compound A-L was the faster hydrolyzed conjugate (half-life=25.4±1.1min). The inhibitory activity of the compounds against SKOV3 ovarian cancer cell growth was analysed. The IC50 values were 7.48±1.27nM for A, 40.3±6.28nM for B, 738±38.5nM for A-L and 37.9±2.11nM for A-L-B. The anticancer effect of A-L-B was evidenced to be obtained via microtubule dynamics suppression. Finally, we stated the expression of the active efflux transporters P-gp (ABCB1) and MRP1 (ABCC1) in the human normal colon epithelial NCM460 cell line by reverse-transcription PCR. Via permeation studies across NCM460 monolayers we demonstrate the poor aptitude of A to interact with active efflux transporters (AET): indeed, the ratio between its permeability coefficients for the basolateral (B)→apical (A) and B→A transport was 1.5±0.1, near to the ratio of taltobulin (1.12±0.06), an hemiasterlin derivative able to elude AETs, and significantly different form the ratio of celiprolol (3.4±0.2), an AET substrate.

Supramolecular hydrogen-bonding patterns of co-crystals containing the active pharmaceutical ingredient (API) phloroglucinol andN-heterocycles

The active pharmaceutical ingredient phloroglucinol (PHL) has been taken as an illustrative molecule to explore the intermolecular interactions which can be established with other molecular entities to build PHL pharmaceutical co-crystals. The crystal structures of five newly synthesized co-crystals are reported, where PHL is crystallized withN-heterocycles, namely 2-hydroxy-6-methylpyridine (1), 2,4-dimethyl-6-hydroxypyrimidine (2), 4-phenylpyridine (3), 2-hydroxypyridine (4) and 2,3,5,6-tetramethylpyrazine (5). The structural characteristics of these co-crystals, as far as the hydrogen-bonding networks and the crystalline architectures are concerned, are strongly dependent on the chemical features of the coformer molecules, as well as on their size and shape. A detailed analysis of the intermolecular interactions established in all the PHL co-crystals of known structures has allowed the recognition of some regularities in the packing modes that can be useful in the design of new supramolecular adducts forming predictable structural motifs.

Cocrystals and alloys of nitazoxanide: enhanced pharmacokinetics

The pharmaceutical cocrystal alloy of NTZ-PABA : NTZ-PASA (0.75 : 0.25) exhibits a higher pharmacokinetic profile than the individual cocrystals and nitazoxanide.