Solifenacin compositions

A process for preparing stabilized solifenacin or a salt thereof, comprising:

• (a) providing a solution containing solifenacin or a salt thereof, a pharmaceutically acceptable carrier, and optionally an antioxidant, then removing solvent or adding an anti-solvent to precipitate a solid;
• or
• (b) providing a solution containing solifenacin or a salt thereof in a nonvolatile solvent, and optionally adsorbing the solution onto a solid pharmaceutical excipient;
• or
• (c) providing a solution containing solifenacin or a salt thereof, and contacting the solution with an insoluble resin to form a resinate;
• or
• (d) providing a solution containing solifenacin or a salt thereof and a cyclodextrin, and combining the solution with a solid pharmaceutical excipient.