Figure 3.

Three main concepts for dissolution from ASDs. (1) In the case of carrier controlled release, drug molecules have to diffuse through the polymer, possibly through a highly viscous gel layer on the surface of ASD particles. If dissolved drug concentrations become high enough to exceed the amorphous solubility, ALPS will occur, inducing the formation of drug-rich particles. (2) In the case of dissolution controlled release, API and polymer dissolve congruently, leading to fast dissolution and formation of drug-rich particles. The polymer may stabilize the supersaturated solution. (3) In the case of drug controlled release, the polymer dissolves out of the ASD and the residual API controls the dissolution rate. If the residual API is not stable in the amorphous state without polymer, i.e. crystallizes, supersaturation will not occur.