ABSTRACT
Irbesartan (IBS) is a tetrazole derivative and antihypertensive drug that has two interconvertible struc-tures, 1H-and 2H-tautomers. The difference between them lies in the protonation of the tetrazole ring. In the solid-state, both tautomers can be isolated as crystal forms A (1H-tautomer) and B (2H-tautomer). Studies have reported that IBS is a polymorphic system and its forms A and B are related monotropically. These reports indicate form B as the most stable and less soluble form. Therefore, the goal of this contribution is to demonstrate through a complete solid-state characterization, thermodynamic study and dissolution properties that the IBS forms are desmotropes that are not related monotropically. However, the intention is also to call attention to the importance of conducting strict chemical and in solid-state quality controls on the IBS raw materials. Hence, powder X-ray diffraction (PXRD) and Raman spectroscopy (RS) at ambient and non-ambient conditions, differential scanning calorimetry (DSC), hot stage microscopy (HSM), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) techniques were applied. Furthermore, intrinsic dissolution rate (IDR) and structural stability studies at 98％relative humidity (RH), 25 ?C and 40 ?C were conducted as well. The results show that in fact, form A is approximately four-fold more soluble than form B. In addition, both IBS forms are stable at ambient conditions. Nevertheless, structural and/or chemical instability was observed in form B at 40 ?C and 98％RH. IBS has been confirmed as a desmotropic system rather than a polymorphic one. Consequently, forms A and B are not related monotropically.
ABSTRACT
To illustrate the intrinsic dissolution rate(IDR) involved in biopharmaceutics classification system of Chinese materia medica(CMMBCS), investigate the effect of artificial multicomponent environment on IDR of berberine, by using a non-disintegrating disk, and summarize related rules by using the obtained data. Progressive levels design was used to investigate the effects of single component environment (puerarin, baicalin, and glycyrrhizic acid); double-component environment(puerarin+baicalin, puerarin+ glycyrrhizic acid, baicalin+glycyrrhizic acid); and triple-component environment(puerarin+baicalin+glycyrrhizic acid) on IDR of berberine, laying a foundation for further researches on the absorption mechanism of multiple components.
ABSTRACT
@#Myricetin(MYR)was cocrystallized with caffeine(CAF)by suspension and the single crystal of MYR-CAF cocrystal was cultured by slow solvent evaporation. Cocrystals obtained by two different methods were the same in crystal form after characterization with X-ray diffraction. Structural analysis of single crystal of MYR-CAF showed that its crystal system and the space group were monoclinic and P21/n, respectively. In MYR-CAF cocrystal, 4′-OH in ring B and 7-OH in ring A of MYR interacted with CAF at(8)C=N and(2)C=O through hydrogen bonds. In comparison to the original MYR crystal, the intrinsic dissolution rate of MYR was significantly enhanced for about 17-fold after cocrystallization with CAF.