Stability and Several Physical Properties of Amorphous and Crystalline Forms of Indomethacin

抄録

An X-ray diffraction method for determination of the degree of crystallinity of indomethacin was established, and the transition rate of indomethacin from amorphous to crystalline form was investigated. The transition of the amorphous form to crystalline form at 20°, 30°and 40°followed first-order kinetics and the Arrhenius plot showed good linearity. The amorphous form was shown to change to form I at 100% relative humidity (RH), to form I or II at 89% RH and to form I at 79% and 69% RH at 30°. The transition rate of the amorphous form to form II at 100% RH was larger than that at 89% RH. A good linear relation was observed between the maximum amount of water absorbed (log scale) and the degree of crystallinity at 100% or 89% RH at 30°. The dissolution rate of the amorphous form was higher than those of forms I and II. The amorphous form showed better tablet-forming properties than the crystalline form.