A Kinetic Study on the Isothermal Transition of Polymorphic Forms of Tolbutamide and Mefenamic Acid in the Solid State at High Temperatures

概要

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The kinetics of the isothermal transition of tolbutamide polymorphic forms (form B at 65,70,75 and 80℃), as well as mefenamic acid (form I at 142.5,145,147.5 and 150℃) were investigated by means of differential scanning calorimetry. Kinetic analysis according to the method of Hancock and Sharp indicated that the transition of form B to form A of tolbutamide proceeds by the mechanism of three-dimensional diffusion (Jander equation). The activation energy for this transition calculated from the slope of the Arrhenius plots was 37.3 kcal/mol. On the other hand, the transition of form I to form II of mefenamic acid appeared to follow the zero-order mechanism (Polany-Winger equation). The activation energy for this transition was calculated to be 86.4 kcal/mol.
公益社団法人日本薬学会の論文
1985-05-25