A process to dehydrate the dihydrate form of a pharmaceutical compound to a crystalline anhydrate form in the solid-state has been developed. An inert gas stream, semi-saturated with solvent is passed continuously through the bed of dihydrate. The degree of dehydration is monitored by PAT in real time to determine the process end point. The effect of solvent type, solvent concentration in the gas stream, and carrier gas flow rate on the rate of form conversion is presented. In the anhydrous state, two enantiotropic polymorphs exist. Polymorph selectivity will also be presented.