Figure 8 shows the change of tablet weight (see Figure 8a) and water-absorbing capacity (see Figure 8b). The water-absorbing
capacity was calculated as a percentage by comparing the tablet weight in the wet state due to water absorption with the tablet
weight in the dry state after drying. During 0–2 h, these matrix tablets absorbed a lot of water, and their weights increased.
After 2 h, the weights of matrix tablets began to decrease in spite of keeping water absorption. The HS tablet with PEG remarkably
absorbed water and lost its weight because the strength of its gel structure weakened.
Figure 9 is a schematic description of the assumed mechanism of different actions between HS and HPMC matrix tablets caused
by promotion of water penetration into tablets by adding PEG. In the case of HS, in the first stage at 0.5–5 h, the hydration
of HS particles was promoted, and a strong gel layer was formed, which contributed to the restraint of drug diffusion. In
the second stage of 6 h and after, excess water absorption occurred because the HS water-insoluble elements absorbed a lot
of water without dissolving, which contributed to decrease gel strength and to promote gel erosion. Accordingly, the drug-release
profiles inclined to zero-order release. In the case of HPMC, the hydration rate of the HPMC particles was not largely affected
by adding PEG because the hydration rate was originally rapid. Therefore, the drug-release profiles remained first order regardless
of adding PEG.
Storage stability study of dissolution profiles and of tablets color. HS or HPMC matrix tablets containing APAP and MCC with or without PEG were used in this study. Table III shows the formulations
of the tablets. These tablets were stored at 40 °C and 75% RH in sealed glass bottles and at 60 °C in polyamine–polyethylene
Figure 10 shows the dissolution profiles at the initial state and after storage for 6 months. The dissolution tests were performed
using a USP Type 1 apparatus at a rotation speed of 100 rpm in a JP-2 buffer containing α-amylase in a 5-µg/L concentration.
For HS matrix tablets, no significant change in release profiles was observed. In contrast, those of HPMC changed under the
Figure 11 shows the change of YI. Under conditions of 40 °C and 75 % RH, the YI of the HS matrix tablets slightly changed,
although that of HPMC remarkably increased. At 60 °C, the YI of both increased, but the YI of the HS matrix tablets after
6 months was the same level with the initial YI of HPMC tablets. In addition, the YI of the HPMC matrix with PEG remarkably
Kazuhiro Obae is a chief engineer in the Ceolus Research and Development Department at Asahi Kasei Chemicals Corporation, 1-105 Kanda Jinbocho, Chiyoda-ku, Tokyo 101-8101 Japan.
Articles by Kazuhiro Obae
Yoshihito Yaginuma is a general manager, all in the Ceolus Research and Development Department at Asahi Kasei Chemicals Corporation.
Articles by Yoshihito Yaginuma
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