Preparation of Phenylbutazone Polymorphs and Their Transformation in Solution

概要

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Polymorphism of phenylbutazone was investigated in detail. Pure α form of phenylbutazone could not be obtained by conventional methods, but it was found that the β form was transformed to the stable α form in ethanol solution at 4℃. At 15 and 25℃, the β form was transformed to a mixture of the α and δ forms, while at 35℃, tha α form in the mixture was converted to the δ form. These results showed that the preparation of a pure polymorphic form by means of recrystallization in solution is not necessarily straightforward. The dissolution bethavior of each form in buffer solution was examined next. The transition temperatures of the pairs of α and δ forms and of α and β forms were 29.0 and 61.6℃, respectively, in buffer solution as determined by means of the non linear van't Hoff model proposed by Grant et al. The heats of fusion of the α, β and δ forms were 8.74,6.48 and 6.85 kcal/mol, and their melting points were 91.2,93.3 and 101.4℃, respectively. These results suggested that the pair of β and δ forms is in a monotropic relation and the pairs of a α and β forms and of α and β forms are in enantiotropic relationships.
公益社団法人日本薬学会の論文
1988-03-25