Abstract: Compositions and methods for administering memantine to a subject are provided. In particular, a solid pharmaceutical composition in a unit dosage form for once daily oral administration is provided. The compositions comprises an extended release formulation of 22.5 mg to 33.75 mg memantine, or a pharmaceutically acceptable salt thereof, wherein administration of a dose of the composition to a human subject provides a mean plasma memantine concentration profile characterized by a change in memantine concentration as a function of time (dC/dT) that is less than 50% of the dC/dT provided by the same quantity of an immediate release form of memantine, determined in a time period between 0 hours to 6 hours after administration of memantine, and wherein dC/dT is measured in a single-dose human PK study. Methods of treating dementia, in particular Alzheimer's diseases, using the compositions are provided.