Interaction of microcrystalline cellulose and water in granules prepared by a high-shear mixer

Stabilization mechanism of limaprost in solid dosage form

The effect of polymeric pharmaceutical excipients on the degradation of limaprost by hydrolysis was assessed by near infrared (NIR) spectroscopy and spin-spin relaxation time (T(2)) measurements of proton NMR. Freeze-dried limaprost-alfadex formulated with various polymeric pharmaceutical excipients was exposed under humidified condition at 25 degrees C and 75% relative humidity. The freeze-dried limaprost-alfadex formulated with cellulose derivatives, hydroxypropylmethylcellulose (HPMC) and hydroxypropylcellulose (HPC-L), degraded easily. However, degradation was suppressed in samples formulated with polysaccharides, dextran40, dextrin, and pullulan, although the water sorption was more than 10% (w/w). A second-derivative NIR study showed the changes in the water mobility in the mixtures. The absorption peak near 1900nm, which was assigned to water with high mobility, was observed in the humidified HPMC and HPC-L. The proton NMR spin-spin relaxation time measurements indicated that the structural relaxation of a polymeric excipient changed upon humidification. The polysaccharides showed only Gaussian relaxations, but the cellulose derivatives showed Lorentzian relaxations and Gaussian relaxations. The T(2) values of the Gaussian relaxation in HPMC and HPC-L were higher than those in dextran40, dextrin, and pullulan throughout the humidifying period. The higher molecular mobility of HPMC and HPC-L is related to the mobility of water, which may accelerate limaprost degradation.

Effect of Moisture on Impact Toughness of Sugar-Coated Tablets Manufactured by the Dusting Method

The purpose of this study was to clarify the effect of moisture on the impact toughness of sugar-coated tablets manufactured by the dusting method. We demonstrated that moisture plays an important role in the impact toughness of sugar-coated tablets. Moisturizing the sugar-coating layer resulted in enhancement of impact toughness of sugar-coated tablets, while reducing moisture in the sugar-coating layer resulted in weakening of the impact toughness. This was due to the characteristics of sucrose, the main ingredient of the sugar-coating layer, which is a soft and non-fragile material at high moisture levels, but hard and fragile at low moisture levels. We also demonstrated that friability as an indicator of impact toughness changed with time, and friability should be measured at 14 d after manufacture. This is due to moisture movement from outer sugar-coating layer into the inner sugar-coated tablets. Incorporating microcrystalline cellulose (MCC) in the subcoating layer resulted in sugar-coating layers with high resistance against impact even though moisture content of sugar-coated tablets was low. We confirmed the high impact toughness of the sugar-coated tablets with MCC whose moisture content was low from the results of both free fall and friability tests. We suggest that the dusting method using dusting powder containing MCC is a useful method for the production of sugar-coated tablets containing moisture sensitive drugs.