The invention is directed to compositions used for treating Central Nervous System (CNS) disorders. In addition, the invention provides convenient methods of treatment of a CNS disorder. Furthermore, the invention provides methods of treating sleep disorders using compositions that remain active for a discrete period of time to reduce side effects. More specifically, the invention is directed to the compositions and use of derivatized, e.g., ester or carboxylic acid derivatized, antihistamine antagonists for the treatment of sleep disorders.