Provided herein are oral pharmaceutical compositions comprising amantadine, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable excipient, and which have a low level of organic solvent. Provided are also methods of orally administrating a composition comprising amantadine, or a pharmaceutically acceptable salt thereof, to a subject, which has reduced gastrointestinal side effects or sleep disturbances. Further provided are extended release oral compositions comprising amantadine, or a pharmaceutically acceptable salt thereof, that are suitable for once daily administration.