Nilvadipine solid dispersions were prepared by the solvent method using water-insoluble polymers, including low-substituted hydroxypropylcellulose, croscarmellose sodium, carmellose calcium, carmellose, and crospovidone. Differential scanning calorimetry and powder x-ray diffraction analysis showed that nilvadipine was present in an amorphous state in the solid dispersion obtained using crospovidone as a carrier. The degree of crystallinity of nilvadipine was dependent on the ratio of nilvadipine to crospovidone, and nilvadipine was present in an amorphous state when the ratio of nilvadipine to crospovidone was below one-half. Fourier transform infrared studies suggested the presence of hydrogen bonding between nilvadipine and crospovidone in the solid dispersion. Dissolution studies indicated that the maximum percentage of dissolution and dissolution rate constants were markedly increased in nilvadipine with crospovidone solid dispersion, compared with those of pure nilvadipine and physical mixtures. The dissolution rate of nilvadipine solid dispersion with crospovidone could be calculated by the Higuchi square root time equation.
Firstly, we investigated the physical stability of nilvadipine (NIL)/crospovidone (cl-PVP) solid dispersion during storage (40 degrees C, 75% relative humidity) with powder x-ray diffraction, differential scanning calorimetry (DSC) and dissolution test. These studies indicated that recrystallization occurred during storage and that the dissolution of NIL greatly decreased, compared with that of the initial finding. Secondly, to improve the amorphous form physical stability of NIL, methylcellulose (MC) was added to NIL/cl-PVP solid dispersions as a dispersion carrier and NIL/cl-PVP/MC ternary solid dispersion systems were obtained by the solvent method. Powder x-ray diffraction and DSC studies indicated that the amorphous form physical stability of NIL clearly improved in the NIL/cl-PVP/MC solid dispersion systems during storage. Moreover, the dissolution properties of NIL/cl-PVP/MC solid dispersion systems were characterized by cl-PVP markedly enhancing the dissolution of NIL and MC inhibiting the change of the dissolution of NIL during storage. Finally, we obtained an ideal solid dispersion that was accompanied by a consistently higher rate of dissolution.
Nilvadipine (NIL) solid dispersion tablets were stored counter to packaging instructions by exposing them to 40°C, 25°C, 75% relative humidity, and light. The dissolution, stability assay, and tablet properties (weight, thickness and hardness) were then examined. NIL dissolved more than 85% after all storage periods with exposure to high temperature and humidity. Powder X-ray diŠraction analysis indicated that NIL was present in an amorphous state as in the initialstate. The stability assay of NIL showed that it was more than 99% stable during all storage periods when exposed to temperature, humidity, and light, indicating good stability. Tablet properties were in‰uenced by humidity more than by temperature, and the hardness of tablets decreased with time to 42.9 N after storage of 3 months. 越化学) ,エタノール(製造用グレード) ,乳糖(ダ
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