In this work, a diffusion-theory-based model has been devised to simulate dissolution kinetics of a poorly water-soluble drug, ibuprofen. The model was developed from the Noyes–Whitney equation in which the dissolution rate term is a function of the remaining particulate surface area and the concentration gradient across the boundary layer. Other dissolution parameters include initial particle size, diffusion coefficient, material density, and diffusion boundary layer thickness. It is useful for predicting nonsink circumstances under which pure API polydisperse powders are suspended in a well-mixing tank. The model was used to compare the accuracy of simulations using spherical (single dimensional characteristic length) and cylindrical particle (multidimensional characteristic lengths) geometries, with and without size-dependent diffusion layer thickness. Experimental data was fitted to the model to obtain the diffusion layer thickness as well as used for model validation and prediction. The CSDs of postdissolution were also predicted with this model, demonstrating good agreement between theory and experiment.

The knowledge of crystallization kinetics, especially crystal nucleation, is crucial for crystallization process design and control. In the present paper, the primary nucleation kinetics of benzoic acid in water−ethanol solution was estimated from induction time measurements, where focused beam reflectance measurement was utilized to detect the onset point of nucleation. As a result, the induction times have been found to decrease with increasing mass fraction of water under the same supersaturation. These data were then used to determine the interfacial energy together with critical size and activation energy for nucleation based on classical nucleation theory. The resulting interfacial energy differed from 1.83 to 6.46 mJ/m 2 at various solvent compositions. Also, it has been demonstrated that the interfacial energy increased with increasing water mass fraction, which finally caused the increase of the critical size and activation energy for nucleation, suggesting significant effects of water mass fraction on nucleation kinetics.

The development of solid dosage forms and manufacturing processes are governed by complex physical properties of the powder and the type of pharmaceutical unit operation the manufacturing processes employs. Suitable powder flow properties and compactability are crucial bulk level properties for tablet manufacturing by direct compression. It is also generally agreed that small scale powder flow measurements can be useful to predict large scale production failure. In this study, predictive multilinear regression models were effectively developed from critical material properties to estimate static powder flow parameters from particle size distribution data for a single component and for binary systems. A multilinear regression model, which was successfully developed for ibuprofen, also efficiently predicted the powder flow properties for a range of batches of two other active pharmaceutical ingredients processed by the same manufacturing route. The particle size distribution also affected the compactability of ibuprofen, and the scope of this work will be extended to the development of predictive multivariate models for compactability, in a similar manner to the approach successfully applied to flow properties.

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