The present invention provides pharmaceutical compositions given once daily containing at least one therapeutically active ingredient selected from the group consisting of memantine and a pharmaceutically acceptable salt of memantine, and a pharmaceutically acceptable polymeric matrix carrier. The dosage forms of the invention sustain the release of the therapeutically active agent from about 4 to about 24 hours when said dosage form is exposed to aqueous solutions. following entry of said form into a use environment, wherein said dosage form has a dissolution rate of more than about 80% after passage of about 6 hours to about 12 hours following said entry into said use environment.