Solid Dispersion, Mathematical Model, Partial Differential Equations, Activity
Coefficients

A solid dispersion is a dosage form in which an active ingredient (a drug) is mixed
with at least one inert solid component. The purpose of the inert component is usually to improve the bioavailability of the drug. In particular, the inert component is frequently chosen to improve the dissolution rate of a drug that is poorly soluble in water. The construction of reliable mathematical models that accurately describe the dissolution of solid dispersions would clearly assist with their
rational design. However, the development of such models is challenging since a dissolving solid dispersion constitutes a non-ideal mixture, and the selection of appropriate forms for the activity
coefficients that describe the interaction between the drug, the inert matrix, and the dissolution medium is delicate. In this paper, we present some preliminary ideas for modelling the dissolution of solid dispersions.