Thermodynamic properties of polymorphic forms of theophylline. Part I: DSC, TG, X-ray study

Polymorphs, Hydrates, Cocrystals, and Cocrystal Hydrates: Thermodynamic Modeling of Theophylline Systems

“…Form II is the usually-available commercial form since it can be easily prepared by crystallization from many organic solvents 80,84 . Thus, form II was long believed to be the thermodynamically stable form at ambient conditions [86][87][88][89] The quality of the modeling was quantitatively evaluated by the average relative deviation (ARD) between the calculated ‫ݔ‬ ݈ܿܽܿ,݅ and experimental solubility ‫ݔ‬ ‫݅,ݔ݁‬ and ݊ ‫ݔ݁‬ being the number of experimental data points: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 In the ternary API/CF/solvent system, the deviation of experimental and calculated data refers to that of the API, in this study TP. The resulting ARDs between the correlated and experimental solubilities of pure components are listed in Tables 1 and 2.…”

Production of theophylline nanoparticles using rapid expansion of supercritical solutions with a solid cosolvent (RESS-SC) technique

“…12 and 13. The morphology of the produced theophylline particles after the vacuum drying was spherical although that of the produced mixture crystals of theophylline and vanillin was agglomerate or fibrous with the mean size of around 1 m. Table 2 shows the melting temperatures and enthalpies of fusion measured using DSC analysis of unprocessed particles, particles produced by RESS-SC and particles produced by RESS [40,41], with those of literature data [51,52]. Comparing between the melting temperature and enthalpy of fusion of unprocessed particles and those of the particles produced by RESS-SC, the melting temperature and enthalpy of fusion of particles produced by RESS-SC was lower than those of unprocessed particles and literature data.…”

“…16 and 17, XRD and FTIR analyses showed that the crystal structure of the theophylline particles did not change after the micronization by RESS-SC and there was no cosolvent (i.e., vanillin) in the crystals produced by RESS-SC because the positions of the peaks in the XRD patterns and FTIR spectra of the unprocessed and the RESS-SC processed theophylline particles are almost the same. Theophylline has one hydrate (Form M) and four anhydrous forms (Forms I-IV) [51][52][53]. The crystal structure of the particles produced was the kinetically stable form at room temperature (Form II).…”

Thermal, spectroscopic, and dissolution studies of the simvastatin–acetylsalicylic acid mixtures

“…Differential scanning calorimetry (DSC) is a widely and effectively used thermal method for solid-state characterization in pharmaceutical preformulation, i.e., eutectic and solid solution formation [28], detection and identification of polymorphic form [29,30], inclusion complexation [31], and compatibility investigation [32,33]. We used DSC, as the main method to investigate the phase equilibrium of that binary system, the knowledge of which is required to determine a eutectic composition.…”