Review of zonisamide development in Japan.

Zonisamide is a benzisoxazole-based compound first synthesized in the early 1970s by the research laboratories of Dainippon Pharmaceutical Company in Osaka, Japan. Identified as an anticonvulsant during exploratory research, zonisamide has since been characterized as having broad-spectrum antiepilepsy and neuroprotective effects. Early clinical studies in Japan demonstrated that zonisamide has a long elimination half-life and is well tolerated; Phase II and III clinical trials established the drug's efficacy and safety for the treatment of partial and generalized seizures. In 1989, zonisamide was approved and marketed in Japan under the trade name of Excegran. Data from postmarketing surveillance studies and clinical observations over 10 years of use have continued to support zonisamide's efficacy and safety, identified its usefulness as monotherapy, and characterized its effectiveness for various seizure types and epilepsy syndromes.