Improving the Solubility, Dissolution, and Bioavailability of Metronidazole via Cocrystallization with Ethyl Gallate

Mechanochemical synthesis of novel metronidazole cocrystal: Structure characterization and pharmaceutical properties study

A new cocrystalline form of metronidazole (MET) with propyl gallate (PRO), referred to as MET-PRO, has been successfully synthesized and characterized. Structural characterization reveals that MET and PRO are present in a 1:1 ratio within the cocrystal lattice, with one water molecule equivalent incorporated into the structure. This arrangement facilitates the formation of MET-PRO heterodimers and multiple stable units, collectively constructing a three-dimensional supramolecular network. The solubility and permeability of the current cocrystal, along with the parent drug MET, are evaluated under physiological pH conditions. Experimental findings reveal that MET within the cocrystal exhibits a 1.54-2.37 folds increase in solubility and approximately a threefold improvement in permeability compared to its standalone form. Intriguingly, these concurrent enhancements in the physicochemical properties of MET lead to augmented antibacterial activity in vitro, evidenced by a reduction in minimum inhibitory concentration. Even more intriguingly, the enhanced physicochemical properties observed in vitro for the current cocrystal translate into tangible pharmacokinetic benefits in vivo, characterized by prolonged half-life and enhanced bioavailability. Consequently, this research not only introduces a fresh crystal structure for antibacterial medication but also presents approach for optimizing drug properties across in vitro and in vivo settings, while concurrently bolstering the antibacterial effectiveness of MET through pharmaceutical cocrystallization techniques.

Supramolecular architectures in multicomponent crystals of imidazole-based drugs and trithiocyanuric acid

The structures of three multicomponent crystals formed with imidazole-based drugs, namely metronidazole, ketoconazole and miconazole, in conjunction with trithiocyanuric acid are characterized. Each of the obtained adducts represents a different category of crystalline molecular forms: a cocrystal, a salt and a cocrystal of salt. The structural analysis revealed that in all cases, the N-H...N hydrogen bond is responsible for the formation of acid-base pairs, regardless of whether proton transfer occurs or not, and these molecular pairs are combined to form unique supramolecular motifs by centrosymmetric N-H...S interactions between acid molecules. The complex intermolecular forces acting in characteristic patterns are discussed from the geometric and energetic perspectives, involving Hirshfeld surface analysis, pairwise energy estimation, and natural bond orbital calculations.

Alfagih I, Al Quadeib BT, Eltahir E, Almarshidy SS, Ibrahim MA, El Sayeh F. Abou El Ela A. Impacts of storage conditions on the dissolution performance of commercial metronidazole tablets available in Saudi Arabia

This study aimed to investigate the impact of storage conditions on the dissolution performance of commercial metronidazole (MTZ) tablets available in Saudi Arabia; these were coded as the reference and Test A, Test B, and Test C products. Moreover, the hardness and the disintegration time were measured. The UV spectrophotometrically analytical technique was utilized to quantify MTZ. All the control tablets, which were tested upon receipt, met the USP requirement as not less than 85 % of the labeled amount of MTZ was dissolved in 60 min. The MTZ reference released 91.79 % ± 1.23 after 60 min, while the products A, B, and C released 87.96 % ± 2.60, 93.26 % ± 2.01, and 88.61 % ± 2.04, respectively. The different dissolution parameters calculated for all the control tablets showed that the MTZ products A and B had optimal dissolution performances and were considered similar to the reference product. The product C showed a significantly reduced dissolution performance and was considered different from the reference. The in vitro dissolution of the MTZ tablets stored at 40oC ± 2 oC/75 % RH ± 5 % for 6 months indicated that the tablets maintained compliance with the USP requirement. The MTZ reference released 89.36 % ± 3.64 after 60 min, while the products A, B, and C released 95.79 % ± 3.91, 88.52 % ± 2.52, and 87.79 % ± 5.04, respectively. However, a slight reduction in the percentage released after 30 min (% DE30) and a slight increase in the mean dissolution time (MDT) were observed during the first 3 months of storage under stressed conditions. These changes were more obvious after 6 months of storage under the same conditions. Furthermore, in vitro dissolution of the product C stored at 40oC ± 2 oC/75 % RH ± 5 % for 3 months with further protection against high humidity revealed an improvement in the dissolution parameters due to the similar protective effects exerted by the two packaging forms. Furthermore, the study shows that storage conditions such as humidity and temperature affect in vitro dissolution of MTZ marketed tablets which may have an impact on efficiency and patient safety.

A new crystalline daidzein-piperazine salt with enhanced solubility, permeability, and bioavailability

To overcome the poor solubility, permeability, and bioavailability of the plant isoflavone daidzein (DAI), a novel salt of DAI with anhydrous piperazine (PIP) was obtained based on cocrystallization strategy. The new salt DAI-PIP was characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, and optical microscopy. The results showed that the maximum apparent solubility (Smax) of DAI-PIP increased by 7.27-fold and 1000-fold compared to DAI in pH 6.8 buffer and water, respectively. The peak apparent permeability coefficient (P app ) of DAI-PIP in the Caco-2 cell model was 30.57 ± 1.08 × 10-6 cm/s, which was 34.08% higher than that of DAI. Additionally, compared to DAI, the maximum plasma concentration (Cmax) value of DAI-PIP in beagle dogs was approximately 4.3 times higher, and the area under the concentration-time curve (AUC0-24) was approximately 2.4 times higher. This study provides a new strategy to enhance the dissolution performance and bioavailability of flavonoid drugs, laying a foundation for expanding their clinical applications.

Metronidazole Cocrystal Polymorphs with Gallic and Gentisic Acid Accessed through Slurry, Atomization Techniques, and Thermal Methods

In this study, key features of metronidazole (MNZ) cocrystal polymorphs with gallic acid (GAL) and gentisic acid (GNT) were elucidated. Solvent-mediated phase transformation experiments in 30 solvents with varying properties were employed to control the polymorphic behavior of the MNZ cocrystal with GAL. Solvents with relative polarity (RP) values above 0.35 led to cocrystal I°, the thermodynamically stable form. Conversely, solvents with RP values below 0.35 produced cocrystal II, which was found to be only 0.3 kJ mol-1 less stable in enthalpy. The feasibility of electrospraying, including solvent properties and process conditions required, and spray drying techniques to control cocrystal polymorphism was also investigated, and these techniques were found to facilitate exclusive formation of the metastable MNZ-GAL cocrystal II. Additionally, the screening approach resulted in a new, high-temperature polymorph I of the MNZ-GNT cocrystal system, which is enantiotropically related to the already known form II°. The intermolecular energy calculations, as well as the 2D similarity between the MNZ-GAL polymorphs and the 3D similarity between MNZ-GNT polymorphs, rationalized the observed transition behaviors. Furthermore, the evaluation of virtual cocrystal screening techniques identified molecular electrostatic potential calculations as a supportive tool for coformer selection.

Development of Composite, Reinforced, Highly Drug-Loaded Pharmaceutical Printlets Manufactured by Selective Laser Sintering-In Search of Relevant Excipients for Pharmaceutical 3D Printing

3D printing by selective laser sintering (SLS) of high-dose drug delivery systems using pure brittle crystalline active pharmaceutical ingredients (API) is possible but impractical. Currently used pharmaceutical grade excipients, including polymers, are primarily designed for powder compression, ensuring good mechanical properties. Using these excipients for SLS usually leads to poor mechanical properties of printed tablets (printlets). Composite printlets consisting of sintered carbon-stained polyamide (PA12) and metronidazole (Met) were manufactured by SLS to overcome the issue. The printlets were characterized using DSC and IR spectroscopy together with an assessment of mechanical properties. Functional properties of the printlets, i.e., drug release in USP3 and USP4 apparatus together with flotation assessment, were evaluated. The printlets contained 80 to 90% of Met (therapeutic dose ca. 600 mg), had hardness above 40 N (comparable with compressed tablets) and were of good quality with internal porous structure, which assured flotation. The thermal stability of the composite material and the identity of its constituents were confirmed. Elastic PA12 mesh maintained the shape and structure of the printlets during drug dissolution and flotation. Laser speed and the addition of an osmotic agent in low content influenced drug release virtually not changing composition of the printlet; time to release 80% of Met varied from 0.5 to 5 h. Composite printlets consisting of elastic insoluble PA12 mesh filled with high content of crystalline Met were manufactured by 3D SLS printing. Dissolution modification by the addition of an osmotic agent was demonstrated. The study shows the need to define the requirements for excipients dedicated to 3D printing and to search for appropriate materials for this purpose.