Zonisamide was discovered by Uno and colleagues in 1972 and launched by Dainippon Sumitomo Pharma (大日本住友製薬,Dainippon Sumitomo Seiyaku?) (formerly Dainippon Pharmaceutical (大日本製薬,Dainippon Seiyaku?)) in 1989 as Excegran in Japan. It was marketed by Élan in the United States starting in 2000 as Zonegran, before Élan transferred their interests in zonisamide to Eisai (エーザイ,Eisai?) in 2004. Eisai also markets Zonegran in Asia (China, Taiwan, and fourteen others) and Europe (starting in Germany and the United Kingdom).
Zonisamide is approved in the United States, United Kingdom, for adjunctive treatment of partial seizures in adults and in Japan for both adjunctive and monotherapy for partial seizures (simple, complex, secondarily generalized), generalized (tonic, tonic-clonic (grand mal), and atypical absence) and combined seizures.
An open trial on zonisamide in seven Parkinson's disease patients had positive results, according to this 2001 report. Since then, it has been reported to treat the resting tremor that other therapies may leave behind. By early November of 2005, Dainippon Sumitomo had filed a NDA for the use of zonisamide in Parkinson's disease; it is to be marketed as Tremode.
It has also been studied for obesity with significant positive effects on body weight and there are three ongoing clinical trials for this indication.
Zonisamide has been studied for and used as a migraine preventative medication, and has also been shown to be effective in some cases of neuropathic pain. It has also been used by psychiatrists as a mood stabilizer.
Zonisamide is metabolized mostly by the CYP3A4 isoenzyme, but also CYP3A7 and CYP3A5, to 2-(sulphamoylacetyl)-phenol via reductive cleavage of the 1,2-benzisoxazole ring.
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