USP dissolution III: semilogarithmic dissolution patterns of tablets in rotating-basket assemblies.

The dissolution of a rapidly soluble, finely subdivided substance in a directly compressed tablet and in a wet granulated tablet was treated experimentally and compared with previous theoretical models. The dissolution curves were sigmoid with a semilogarithmic tail when concentration was plotted versus time. As predicted, the slope of the semilogarithmic plots were related to the disintegration decay constant for tablet erosion in the basket.