As disclosed herein, co-administration of pimavanserin with an agent that ameliorates one or more cholinergic abnormalities can have a synergistic effect on the efficacy of the agent. Disclosed herein are compositions which include pimavanserin in combination with an agent that ameliorates one or more cholinergic abnormalities. Also disclosed herein are methods for ameliorating or treating a disease condition characterized by one or more cholinergic abnormalities that can include administering pimavanserin in combination with an agent that ameliorates one or more cholinergic abnormalities.
