This study evaluated the effects of changing the amount of added water for moisture activated dry granulation (MADG) on the resulting granule characteristics and tablet properties. Water soluble fillers and binders were pre-mixed in a granulator, and the binder was activated by a small amount of water to form granules. The amount of added water was defined as the percentage of granulation water by mass to charged powder. Granules made with 0.0%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 5.0% (w/w) added water were evaluated in this study. Furthermore, the effect of free water content on tablet characteristics was investigated by measuring water activity.

The Hausner ratio (HR) of MADG granules is significantly decreased by increasing the amount of added water up to 1.0% (water activity over 0.39). However, the HR of MADG granules did not change with further increase in water activity (added water over 2.5%). The free water content (water activity over 0.61, water added over 2.5%) may reach a limit in improving the flowability of MADG granules.

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