Physical characterization of picotamide monohydrate and anhydrous picotamide

Solid Forms of The New Antitrypanosomal 1-(4-Acetamide-Benzenesulfonyl)-Benzimidazole: Preparation and Physicochemical Characterization

This study aimed to investigate the polymorphism of 1-(4-acetamide-benzenesulfonyl)-benzimidazole (PABZI), a newly developed compound with significant activity against Trypanosoma cruzi, the parasite which causes American trypanosomiasis (Chagas disease). Three different crystalline forms of PABZI [a solvent-free form (form I), three isostructural solvates (from isopropanol; acetonitrile-dichloromethane, and methanol-benzene) and a non-isostructural solvate from methanol] were isolated and characterized. The crystal structure of form I was resolved at 173 K and 300 K by single crystal X-ray diffraction. Physicochemical properties, including solubility, dissolution rate, wettability, and solid-state stability were assessed for the two most viable solid forms of PABZI, viz. form I and the isopropanol solvate (PABZI-isoOH). Form I exhibited a higher solubility and dissolution rate, and superior stability towards moisture (40 °C/75 % relative humidity) and UV-Visible light than PABZI-isoOH. Based on the solid-state stability results, form I was selected over PABZI-isoOH for further preclinical studies.

Evidence of Polymorphism on the Antitrypanosomal Naphthoquinone (4E)-2-(1H-Pyrazol-3-ylamino)-4-(1H-pyrazol-3-ylimino)naphthalen-1(4H)-one

The aim of this study was to characterize the solid state properties of (4E)-2-(1H-pyrazol-3-ylamino)-4-(1H-pyrazol-3-ylimino)naphthalen-1(4H)-one (BiPNQ), a compound with a significant inhibitory activity against Trypanosoma cruzi, the etiological agent of Chagas disease (American trypanosomiasis). Methods used included Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Fourier Transform Infrared Spectroscopy (FTIR), Powder X-Ray Diffraction (PXRD), Hot Stage, and Confocal Microscopy. Two BiPNQ samples were obtained by crystallization from absolute methanol and 2-propanol-water that exhibited different thermal behaviours, PXRD patterns, and FTIR spectra, indicating the existence of an anhydrous form (BiPNQ-I) and a solvate (BIPNQ-s), which on heating desolvated leading to the anhydrous modification BiPNQ-I. It was determined that FTIR, DSC, and PXRD are useful techniques for the characterization and identification of the crystalline modifications of BiPNQ.

Structural characterisation and dehydration behaviour of siramesine hydrochloride

In this study the crystal structures of siramesine hydrochloride anhydrate alpha-form and siramesine hydrochloride monohydrate were determined, and this structural information was used to explain the physicochemical properties of the two solid forms. In the crystal structure of the monohydrate, each water molecule is hydrogen bonded to two chloride ions, and thus the water is relatively strongly bound in the crystal. No apparent channels for dehydration were observed in the monohydrate structure, which could allow transmission of structural information during dehydration. Instead destructive dehydration occurred, where the elimination of water from the monohydrate resulted in the formation of an oily phase, which subsequently recrystallised into one or more crystalline forms. Solubility and intrinsic dissolution rate of the anhydrate alpha-form and the monohydrate in aqueous media were investigated and both were found to be lower for the monohydrate compared to the anhydrate alpha-form. Finally, the interactions between water molecules and chloride ions in the monohydrate as well as changes in packing induced by water incorporation could be detected by spectroscopic techniques.

Solid state characterization of mometasone furoate anhydrous and monohydrate forms

Mometasone furoate is a potent glucocorticoid anti-inflammatory agent. Its anhydrous Form 1 and monohydrate form were characterized by X-ray crystallography, X-ray powder diffraction at ambient and elevated temperature, thermal analysis, FT-IR, and dynamic moisture adsorption. In Form 1, mometasone furoate molecules pack tightly with molecules interlocked in a space group of P2(1)2(1)2(1). The monohydrate form crystallizes in space group P1. The unit cell of the monohydrate contains one water molecule and one mometasone furoate molecule. The water molecules form channels along the a axis and mometasone furoate molecules pack in layers in the same direction. Dehydration was observed between 60 and 100 degrees C by thermogravimetric analysis with a heating rate of 10 degrees C/min. It corresponds to a broad endotherm over the same temperature range in the differential scanning calorimetry with the same heating rate. Variable temperature X-ray powder diffraction reveals that a new anhydrous form (Form 2) was fully produced above 90 degrees C. This crystalline form was converted to Form 1 after being heated above 150 degrees C; and was totally converted to the monohydrate after 1 day at 23 degrees C, 45% RH.

Solubility and Prediction of the Heat of Solution of Sodium Naproxen in Aqueous Solutions

The solubility of sodium naproxen was determined over a range of temperatures from 15.2 degrees C to 39.7 degrees C by two methods: analyses of samples from equilibrated solutions and a recently developed procedure utilizing a focused-beam reflectance method (FBRM). The results demonstrate the utility of the newer and, in some cases, simpler method. A discontinuity in the solubility was observed at 29.8 degrees C, identifying the temperature as which the dihydrate and anhydrous forms of sodium naproxen trade places as being the more stable of the two forms. The heats of solution for the two pseudopolymorphs were obtained from van't Hoff plots of the solubility data. These results were used to demonstrate how the heat of solution of one form can be estimated using the heat of dehydration obtained from differential scanning calorimetry (DSC) and the heat of solution from another form.

Physicochemical analyses of phase transition and dehydration processes of a new oral 1beta-methylcarbapenem antibiotic agent, CS-834

The characterizations of the anhydrate (A-form), monohydrate (B1-form), and dihydrate (B2-form) of CS-834 were investigated by powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA), infrared spectroscopy, and Karl Fischer moisture titration. The typical DSC curve of the B2-form showed five endothermic peaks at 35.0, 46.4, 56.2, 99.2, and 190.4 degrees C and an exothermic peak at 123.4 degrees C. In TG-DTA analysis, the three peaks at 35.0, 46.4, and 56.2 degrees C had a total weight loss of 7.3%, corresponding to the release of two water molecules. From morphological observation under thermomicroscopy, the endothermic peak at 99.2 degrees C was attributed to the melting of the dehydrous crystals (B0-form) and the exothermic peak at 123.4 degrees C to the recrystallization to the A-form crystals. The endothermic peak at 190.4 degrees C was due to the melting of the A-form crystals. After incubation for 6.0 h at 35, 50, 60, and 80 degrees C, the powder X-ray diffraction patterns of the B2-form indicated that it was converted into the A-form via the B1-form and B0-form. Thus CS-834 exists in homologous hydrous crystal forms in multiple-phase transformations with the dehydration of two water molecules.

Solid state characterization of E2101, a novel antispastic drug

E2101, a novel antispastic drug, was found to exist in at least two polymorphs that were confirmed by X-ray powder diffraction (XRD). These two species are designated forms I and II. The physicochemical and thermodynamic properties of these polymorphs were characterized by variable temperature XRD, thermal analysis, hygroscopicity measurements, and dissolution studies. The transition temperature was also estimated from the solubilities determined at various temperatures. The E2101 polymorphs were anhydrous and adsorbed little moisture under high humidity conditions. The melting onsets and heats of fusion for form I were 148.1 +/- 0.2 degrees C and 38.2 +/- 1.0 kJ/mol, respectively, and for form II were 139.8 +/- 0.4 degrees C and 35.2 +/- 0.5 kJ/mol, respectively. The intrinsic dissolution rate of form II in JP 2 medium was 1.5-fold faster than that of form I, corresponding to the rank order of the aqueous solubility and the enthalpy of fusion. Accordingly, form I was thought to be thermodynamically more stable than form II and thus suitable for further development. According to the thermal analysis and variable temperature XRD results, the recrystallization of form I occurred at approximately 145 degrees C after form II melted, however, no crystal transition behavior was observed below the lower melting point. The DSC thermograms at various heating rates and van't Hoff plots from the solubility studies indicated that the polymorphic pair would be monotropic.

Characterization of azithromycin hydrates

Azithromycin (AZI) is a macrolide antibiotic with an expanded spectrum of activity that is commercially available as a dihydrate. This study was carried out to characterize hydrates of azithromycin. A commercial dihydrate sample was used to prepare monohydrate from water/ethanol (1:1) mixture. Hydrates were characterized using DSC, TGA, KFT, XRD, HSM, SEM and FT-IR. TGA showed that the commercial samples are dihydrate and the sample prepared from water/ethanol (1:1) was a monohydrate. Solubility studies revealed that monohydrate converted to dihydrate during solubility studies and as a result there was no significant difference in the equilibrium solubility of MH and DH. Thermal analysis under various conditions revealed that dehydration and melting took place simultaneously. Anhydrous AZI was found to be hygroscopic and converted to DH on storing at room temperature. Molecular modeling studies revealed the probable sites of attachment of water molecules to AZI.

Physical characterization of naproxen sodium hydrate and anhydrate forms

Naproxen sodium (NS) is a nonsteroidal anti-inflammatory drug used in painful and inflammatory diseases. By crystallization from water or by exposure to relative humidities over 43%, the anhydrate form can be hydrated to a dihydrate species. Different techniques have been used to characterize physically anhydrate naproxen sodium (ANS) and hydrate naproxen sodium (HNS): elemental analysis, atomic absorption, electron scanning microscopy, thermomicroscopy, differential scanning calorimetry, Karl Fisher's titrimetry, thermogravimetry, spectrophotometric analysis and X-ray diffraction study. The hydration/dehydration mechanism, at different relative humidities, was investigated to evaluate their physical stability. When stored up to 43% relative humidity, ANS shows a good stability, whereas with an increase in relative humidity it is hydrated. HNS equilibrium solubility was determined at different temperatures (21, 26, 31, and 37 degrees C). Due to the metastability and the quick phase changes in the water of ANS, its solubility was calculated from intrinsic dissolution measurements at the same temperatures, as solubility measurements of HNS. Water solubility of ANS is greater than HNS, but the solubility difference decreases when the temperature decreases. This is due to the fact that at higher temperatures the intrinsic dissolution rates (IDR) of ANS are considerably faster and decrease as the temperature falls.