The role of a polymer as coformer is not a well-explored area for pharmaceutical co-crystals. To investigate this class of materials, a series of seven co-crystals, which are composed of dapsone and polyethylene glycol are reported. A promising strategy for fine-tuning physicochemical properties namely, crystallinity, thermal stability, hygroscopicity, and solubility was discussed via an in-depth structural understanding. Molecular insights into drug–polymer interactions and co-crystal formation are elaborated from the single crystal X-ray structure determination, Fourier transform infrared spectroscopy, differential scanning calorimetry, and hot-stage microscopy studies.

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Aims:Carvedilol phosphate (CDP) is a nonselective beta-blocker used for the treatment of heart failures and hypertension. In this work, moisture sorption–desorption characteristics and thermodynamic properties of CDP have been investigated.Materials and Methods:The isotherms were determined using dynamic vapor sorption analyzer at different humidity conditions (0%–90% relative humidity) and three pharmaceutically relevant temperatures (20°C, 30°C, and 40°C). The experimental sorption data determined were fitted to various models, namely, Brunauer–Emmett–Teller; Guggenheim-Anderson-De Boer (GAB); Peleg; and modified GAB. Isosteric heats of sorption were evaluated through the direct use of sorption isotherms by means of the Clausius-Clapeyron equation.Statistical Analysis Used:The sorption model parameters were determined from the experimental sorption data using nonlinear regression analysis, and mean relative percentage deviation (P), correlation (Correl), root mean square error, and model efficiency were considered as the criteria to select the best fit model.Results:The sorption–desorption isotherms have sigmoidal shape – confirming to Type II isotherms. Based on the statistical data analysis, modified GAB model was found to be more adequate to explain sorption characteristics of CDP. It is noted that the rate of adsorption and desorption is specific to the temperature at which it was being studied. It is observed that isosteric heat of sorption decreased with increasing equilibrium moisture content.Conclusions:The calculation of the thermodynamic properties was further used to draw an understanding of the properties of water and energy requirements associated with the sorption behavior. The sorption–desorption data and the set of equations are useful in the simulation of processing, handling, and storage of CDP and further behavior during manufacture and storage of CDP formulations.

a b s t r a c tObjective: In the present study, simultaneous determination of degree of crystallinity content in abacavir (ABC), lamivudine (3TC) and neverapine (NVP) from there combination drug product using X-ray powder diffraction (XRPD) technique is developed and validated. Methods: The X-ray procedure for the identification and determination of the degree of crystallinity in ABC, 3TC and NVP drug product is developed and validated. It is based on the X-ray diffraction from crystalline region of the drug product. The characteristic peaks of the three drugs were characterized using XRPD. Results: ABC, 3TC and NVP concentrations ranging from 70% to 130% in drug product were prepared and linearity in this concentration range is described. The % coefficient of variation (%CV) was found to be 0.9982 for ABC, 0.9978 for 3TC and 0.9984 for NVP. The mean recoveries were found to be 100.3% for ABC, 99.0% for 3TC and 100.8% for NVP. Regressions statistics and Analysis of variance (ANOVA) table results were evaluated and found to be satisfactory. Conclusions: The method has been applied to unknown mixtures of drug formulations and stability samples. The proposed method can be useful in the quality control of combination drug products.