Zonisamide

Chemical compound

Drugbox
| verifiedrevid = 477869643
| image = Zonisamide structure. svg
| alt =
| image2 = Zonisamide molecule ball. png
| alt2 = Ball and stick model of the zonisamide molecule

| tradename = Zonegran, Zonisade
| Drugs. com =
| MedlinePlus = a603008
| DailyMedID = Zonisamide
| pregnancy AU = D
| routes of administration = By mouth
| ATC prefix = N03
| ATC suffix = AX15

| legal AU = S4
| legal AU comment =
| legal CA = Rx only
| legal UK = POM
| legal US = Rx only
| legal US comment =
| legal EU = Rx only

| bioavailability = ~100% Chemically it is a sulfonamide. It serves as an anticonvulsant used primarily as an adjunctive therapy in adults with Parkinson's disease, partial onset seizures; infantile spasm, mixed seizure types of Lennox–Gastaut syndrome, myoclonic and generalized tonic clonic seizure. Despite this it is also sometimes used as a monotherapy for partial onset seizures.

Zonisamide is approved in the United States, and United Kingdom for adjunctive treatment of partial seizures in adults and 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. In Australia it is marketed as both an adjunctive therapy and monotherapy for partial seizures only. In addition, there is clinical evidence that zonisamide in combination with levodopa control of motor symptoms of PD but evidence for the treatment of the non motor symptoms of PD lacking.

Zonisamide and other carbonic anhydrase inhibitors such as topiramate, furosemide, and hydrochlorothiazide have been known to interfere with amobarbital, which has led to inadequate anesthetization during the Wada test. Zonisamide may also interact with other carbonic anhydrase inhibitors to increase the potential for metabolic acidosis. Zonisamide is not known to inhibit cytochrome P450 enzymes when present at therapeutic concentrations.

Zonisamide is an antiseizure drug chemically classified as a sulfonamide and unrelated to other antiseizure agents. The precise mechanism by which zonisamide exerts its antiseizure effect is unknown, although it is believed that the drug blocks sodium and T type calcium channels, which leads to the suppression of neuronal hypersynchronization (that is, seizure form activity).

Variable, yet relatively rapid rate of absorption with a time to peak concentration of 2.8–3.9 hours. Bioavailability is close to 100% and food has no effect on the bioavailability of zonisamide but may affect the rate of absorption. to 2 (sulphamoylacetyl) phenol via reductive cleavage of the 1,2 benzisoxazole ring.

Zonisamide was discovered by Uno and colleagues in 1972 and launched by Dainippon Sumitomo Pharma (formerly Dainippon Pharmaceutical) 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 Co., Ltd. in 2004. Eisai also markets Zonegran in Asia (China, Taiwan, and fourteen others) and Europe (starting in Germany and the United Kingdom).

In an open label trial zonisamide attenuated the symptoms of tardive dyskinesia.

It has also been studied for obesity with significant positive effects on body weight loss and there are three ongoing clinical trials for this indication. It was to be sold, when combined with bupropion, under the brand name Empatic, until its development was discontinued.

Zonisamide has been studied for and used as a migraine preventative medication, when topiramate is either ineffective or cannot be continued due to side effects.