Model systems for dissolution of finely divided (multisized) drug powders

Several reports have dealt with model systems for the dissolution of log-normally distributed powders. A numerical solution is presented for the previously published Higuchi-Hiestand equations for a log-normal particle-size distribution. This solution was realized via an application of the System 360 Continuous System Modeling Program (CSMP). The resulting computer-aided calculations were utilized in the comparisons between the Higuchi-Hiestand model and other existing models. These comparisons provided a basis for the development of an adaptation of the Nielsen moving sphere model for log-normally distributed powders. The adaptation of the Nielsen equation for multisized particle systems is suggested as being potentially useful for treating experimental data where hydrodynamic effects must be considered.