In 2020, it was the 276th most commonly prescribed medication in the United States, with more than 1million prescriptions.[10][11]
Medical uses
Epilepsy
Zonisamide is approved in the United States,[2][12] and United Kingdom[13] 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.[14] In Australia it is marketed as both an adjunctive therapy and monotherapy for partial seizures only.[9]
Parkinson's disease
It has been approved for the treatment of the motor symptoms of Parkinson's disease (PD), as an adjunct to levodopa, in a few countries such as Japan.[6][7] In Japan, zonisamide has been used as an adjunct to levodopa treatment since 2009.[15] 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.[16][17]
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.[21] Zonisamide may also interact with other carbonic anhydrase inhibitors to increase the potential for metabolic acidosis.[5]
Zonisamide is not known to inhibit cytochrome P450 enzymes when present at therapeutic concentrations.[23]
Mechanism of action
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).[9] It is also known to be a weak carbonic anhydrase inhibitor (similarly to the anticonvulsant topiramate). It is also known to modulate GABAergic and glutamatergic neurotransmission.[9][24][25][26][27]
Pharmacokinetics
Absorption
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.[28][23]
Zonisamide was discovered by Uno and colleagues in 1972[31] and launched by Dainippon Sumitomo Pharma (formerly Dainippon Pharmaceutical) in 1989 as Excegran in Japan.[32] 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.[33] Eisai also markets Zonegran in Asia (China, Taiwan, and fourteen others)[34] and Europe (starting in Germany and the United Kingdom).[35]
It has also been studied for obesity[37] with significant positive effects on body weight loss and there are three ongoing clinical trials for this indication.[38][39][40] It was to be sold, when combined with bupropion, under the brand name Empatic, until its development was discontinued.[41]
Migraine
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.[7]
Bipolar depression
It has also been used off-label by psychiatrists as a mood stabilizer to treat bipolar depression.[42][43]
^"Zonegran EPAR". European Medicines Agency. 10 March 2005. Retrieved 24 May 2024.
^ abcdefg"Zonegran Product Information"(PDF). TGA eBusiness Services. SciGen (Australia) Pty Ltd. 4 April 2013. Archived from the original on 15 October 2018. Retrieved 18 November 2013.
^Matsunaga S, Kishi T, Iwata N (2017). "Combination Therapy with Zonisamide and Antiparkinson Drugs for Parkinson's Disease: A Meta-Analysis". Journal of Alzheimer's Disease. 56 (4): 1229–1239. doi:10.3233/JAD-161068. PMID28157097.
^Karaduman AB, Kilic V, Atli-Eklioglu O, Baysal M, Aydogan-Kılıc G, Ucarcan S, et al. (December 2019). "Reproductive toxic effects and possible mechanisms of zonisamide in male rats". Human & Experimental Toxicology. 38 (12): 1384–1396. Bibcode:2019HETox..38.1384K. doi:10.1177/0960327119871094. PMID31476894. S2CID201804214.
^Mimaki T, Suzuki Y, Tagawa T, Karasawa T, Yabuuchi H (March 1990). "Interaction of zonisamide with benzodiazepine and GABA receptors in rat brain". Medical Journal of Osaka University. 39 (1–4): 13–7. PMID1369646.
^Mimaki T, Suzuki Y, Tagawa T, Karasawa T, Yabuuchi H (March 1990). "[3H]zonisamide binding in rat brain". Medical Journal of Osaka University. 39 (1–4): 19–22. PMID1369647.
^Ueda Y, Doi T, Tokumaru J, Willmore LJ (August 2003). "Effect of zonisamide on molecular regulation of glutamate and GABA transporter proteins during epileptogenesis in rats with hippocampal seizures". Brain Research. Molecular Brain Research. 116 (1–2): 1–6. doi:10.1016/S0169-328X(03)00183-9. PMID12941455.
^"Zonisamide". www.drugbank.ca. Archived from the original on 2019-01-31. Retrieved 2019-01-31.
^Ohmori S, Nakasa H, Asanome K, Kurose Y, Ishii I, Hosokawa M, et al. (May 1998). "Differential catalytic properties in metabolism of endogenous and exogenous substrates among CYP3A enzymes expressed in COS-7 cells". Biochimica et Biophysica Acta (BBA) - General Subjects. 1380 (3): 297–304. doi:10.1016/s0304-4165(97)00156-6. PMID9555064.
^Stiff DD, Robicheau JT, Zemaitis MA (January 1992). "Reductive metabolism of the anticonvulsant agent zonisamide, a 1,2-benzisoxazole derivative". Xenobiotica. 22 (1): 1–11. doi:10.3109/00498259209053097. PMID1615700.
^Shah J, Kent S, Daniel MC (2002-06-15) [1972]. "Zonisamide". In René H, Levy RH, Brian SM, Perrucca E (eds.). Antiepileptic Drugs (Fifth ed.). Philadelphia: Lippincott Williams & Wilkins. p. 873. ISBN0-7817-2321-3. Archived from the original on 2021-08-27. Retrieved 2007-11-07.
^Dainippon Sumitomo Pharma Co. Ltd. (2005). "Company History". Company Information. Dainippon Sumitomo Co., Ltd. Archived from the original on 13 February 2006. Retrieved 12 November 2005.
^"Bupropion/zonisamide". AdisInsight. Springer. 20 May 2017. Archived from the original on 19 August 2017. Retrieved 19 August 2017.
^Loftus BD (2004). "Zonegran". Archived from the original on 2008-10-23. Retrieved 2006-11-29.
^Hasegawa H (May 2004). "Utilization of zonisamide in patients with chronic pain or epilepsy refractory to other treatments: a retrospective, open label, uncontrolled study in a VA hospital". Current Medical Research and Opinion. 20 (5): 577–80. doi:10.1185/030079904125003313. PMID15140322. S2CID43580909.