Zonisamide

What it is and how it works

Mechanism of Action The precise mechanism(s) by which zonisamide exerts its antiseizure effect is unknown. Zonisamide demonstrated anticonvulsant activity in several experimental models. In animals, zonisamide was effective against tonic extension seizures induced by maximal electroshock but ineffective against clonic seizures induced by subcutaneous pentylenetetrazol. Zonisamide raised the threshold for generalized seizures in the kindled rat model and reduced the duration of cortical focal seizures induced by electrical stimulation of the visual cortex in cats.

Mechanism class: Carbonic Anhydrase Inhibitors · P-Glycoprotein Inhibitors

Indications

INDICATIONS AND USAGE Zonisamide capsules are indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.

Dosage and administration (summary)

DOSAGE AND ADMINISTRATION Zonisamide capsules are recommended as adjunctive therapy for the treatment of partial seizures in adults. Safety and efficacy in pediatric patients below the age of 16 have not been established. Zonisamide capsules should be administered once or twice daily, using 25 mg, 50 mg or 100 mg capsules. Zonisamide capsules are given orally and can be taken with or without food. Capsules should be swallowed whole. Adults over Age 16 The prescriber should be aware that, because of the long half-life of zonisamide, up to two weeks may be required to achieve steady state levels upon reaching a stable dose or following dosage adjustment.

Contraindications

CONTRAINDICATIONS Zonisamide capsules are contraindicated in patients who have demonstrated hypersensitivity to sulfonamides or zonisamide.

Warnings and precautions

WARNINGS Potentially Fatal Reactions to Sulfonamides: Fatalities have occurred, although rarely, as a result of severe reactions to sulfonamides (zonisamide is a sulfonamide) including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Such reactions may occur when a sulfonamide is readministered irrespective of the route of administration. If signs of hypersensitivity or other serious reactions occur, discontinue zonisamide immediately.

Pregnancy

Pregnancy: (see WARNINGS, Teratogenicity subsection): Zonisamide may cause serious adverse fetal effects, based on clinical and nonclinical data. Zonisamide was teratogenic in multiple animal species. Zonisamide treatment causes metabolic acidosis in humans. The effect of zonisamide induced metabolic acidosis has not been studied in pregnancy.

Storage and supply

HOW SUPPLIED Zonisamide capsules USP, 100 mg are white to off white granular powder filled in size '1' hard gelatin capsules with pink colored cap printed with "ZA-33" in black ink and white colored body printed with "100 mg" in black ink, which are supplied as follows.

Source: Zonisamide (Zonisamide) — US FDA prescribing information, 2025-08-01, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.