Effects of compression on the interaction between 1,4-dihydropyridine compounds and lactose monohydrate (II): differences in powder properties of 1,4-dihydropyridine compounds.

The solid-state interaction between manidipine dihydrochloride (Man) or benidipine hydrochloride (Ben) and lactose monohydrate (Lac) was investigated. An endothermic peak area at 170 degrees C was observed when their mixtures were subjected to differential scanning calorimetry (DSC) measurement, and this interaction was accelerated by compression. In the present study, dependency on the particle size of Lac was examined in this solid-state interaction. The DSC peak area at 170 degrees C as a function of the compression force profile was influenced by different particle sizes of Lac in combination with the two medicinal compounds in a different manner. The profile of the onset temperature of Lac dehydration, which indicates the degree of crystalline structure disruption, changed with differing Lac particle size. Moreover, when the particle size of Lac was large, the dehydration onset temperature of Lac with Man decreased from the lower compression force than that of Lac with Ben. The reason for this is thought to be the difference in the powder properties between Man and Ben, although the physicochemical properties of Man and Ben are similar.