Headquartered in Tokyo, Japan, Eisai Co., Ltd. is a pharmaceutical company that develops and markets a diverse range of medicinal products within Japan. Its extensive product lineup includes treatments for neurological conditions, such as Aricept for Alzheimer's disease and Lewy body dementia, Methycobal for peripheral neuropathy, and Fycompa, an antiepileptic drug for specific partial-onset and generalized tonic-clonic seizures. Eisai also offers Dayvigo, an anti-insomnia agent for adults.