ZONISAMIDE-13C2-15N

Zonisamide-¹³C₂,¹⁵N is intended for use as an internal standard for the quantification of zonisamide by GC- or LC-MS. Zonisamide is an antiepileptic agent. It selectively inhibits the repeated firing of sodium channels (IC₅₀ = 2 μg/ml) in mouse embryo spinal cord neurons and inhibits spontaneous channel firing when used at concentrations greater than 10 μg/ml. In rat cerebral cortex neurons, zonisamide (1-1,000 μM) inhibits T-type calcium channels with a maximum reduction of 60% of the calcium current. Zonisamide inhibits H. pylori recombinant carbonic anhydrase (CA) and the human CA isoforms I, II, and V with K_i values of 218, 56, 35, and 21 nM, respectively. In mice, it has anticonvulsant activity against maximal electroshock seizure (MES) and pentylenetetrazole-induced maximal, but not minimal, seizures (ED₅₀s = 19.6, 9.3, and >500 mg/kg, respectively). Zonisamide (40 mg/kg, p.o.) prevents MPTP-induced decreases in the levels of dopamine , but not homovanillic acid (HVA; ) or dihydroxyphenyl acetic acid (DOPAC; ), and increases MPTP-induced decreases in the dopamine turnover rate in mouse striatum in a model of Parkinson''s disease. Formulations containing zonisamide have been used in the treatment of partial seizures in adults with epilepsy.