What is Zonegran?
Zonegran (zonisamide) is a broad-spectrum antiepileptic drug (AED) chemically classified as a sulfonamide, approved as adjunctive therapy for refractory partial seizures in adults. 1
Drug Classification and Mechanism
Zonegran contains zonisamide (1,2-benzisoxazole-3-methanesulfonamide), which is structurally distinct from other antiepileptic medications and unrelated to other antiseizure agents. 1, 2 The drug has multiple complementary mechanisms of action that likely contribute to its efficacy across a broad range of epilepsy types, including modulation of voltage-gated sodium channels. 2, 3
Clinical Indications
- Primary indication: Adjunctive treatment of partial seizures in adults with epilepsy 1, 4
- Not approved for children: Safety and efficacy have not been established in patients under 16 years of age 1
- Broader use in Japan: Extensively used for both partial and generalized seizures in adults and children, including various pediatric epilepsy syndromes 5
Pharmacokinetic Properties
Zonisamide has a long half-life enabling once-daily dosing, with linear pharmacokinetics and minimal drug interactions. 2 Plasma levels of commonly administered AEDs and oral contraceptives remain unaffected by concomitant zonisamide administration. 2
Efficacy Profile
Effective seizure control is achieved at doses ≥300 mg/day, with studies demonstrating up to 51% decrease in seizure frequency for partial seizures. 2, 6 In pivotal trials, zonisamide 500 mg/day showed significant superiority over placebo in reducing complex partial seizures (-51% versus -16%). 6
Critical Safety Warnings
Life-Threatening Reactions
Serious skin reactions and hypersensitivity: Zonegran can cause severe, potentially fatal reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS). 1 Patients should immediately contact their provider if they develop fever, severe muscle pain, rash, swollen lymph glands, facial swelling, unusual bruising/bleeding, weakness, fatigue, or yellowing of skin/eyes. 1
Thermoregulation Issues
Zonegran may cause decreased sweating and increased body temperature (hyperthermia), particularly in hot weather and in children. 1 This can require hospitalization and patients must watch for high fever, recurring fever, or reduced sweating. 1
Ophthalmologic Emergencies
The drug can cause acute myopia and secondary angle-closure glaucoma, presenting as sudden vision decrease with or without eye pain and redness. 1 These complications can lead to permanent vision loss if untreated and require immediate medical attention. 1
Psychiatric and Suicidal Risk
Like other antiepileptic drugs, Zonegran carries a risk of suicidal thoughts or actions (approximately 1 in 500 patients). 1 Warning signs include thoughts about suicide, new or worsening depression, anxiety, agitation, panic attacks, insomnia, irritability, aggression, or unusual behavioral changes. 1
Metabolic Complications
Zonegran increases blood acid levels (metabolic acidosis), which if untreated can cause osteoporosis, osteomalacia, osteopenia, kidney stones, and slowed growth in children. 1 Blood acid levels should be monitored before and during treatment. 1
Additional Serious Risks
- Kidney stones: Back pain, stomach pain, or blood in urine may indicate nephrolithiasis 1
- Blood cell changes: Reduced red and white blood cell counts can occur 1
- Cognitive effects: Problems with concentration, attention, memory, thinking, speech, or language 1
- Hyperammonemia: High blood ammonia levels affecting mental activities and alertness 1
Contraindications and Precautions
Absolute contraindication: Allergy to sulfa-containing medications 1
Zonegran should not be stopped abruptly as this can cause status epilepticus (seizures that will not stop). 1 Patients must avoid alcohol and sedating drugs until discussing with their provider, as Zonegran can potentiate sedation and dizziness. 1 The drug may impair driving ability and operation of heavy machinery. 1
Special Populations
Pregnancy: Zonegran may harm the unborn baby; women of childbearing potential should use effective birth control. 1 Pregnant patients should be enrolled in the North American Antiepileptic Drug Pregnancy Registry (1-888-233-2334). 1
Breastfeeding: Zonisamide passes into breast milk with unknown effects on infants. 1
Formulation and Administration
Available as oral capsules in 25 mg and 100 mg strengths containing zonisamide plus inactive ingredients (microcrystalline cellulose, hydrogenated vegetable oil, sodium lauryl sulfate, gelatin, titanium dioxide, and colorants in 100 mg capsules). 1 Capsules should be swallowed whole with or without food. 1
Important Note on Drug Name Confusion
The expanded question incorrectly identifies Zonegran as levetiracetam—these are completely different medications. Zonegran contains zonisamide, not levetiracetam (which is marketed as Keppra). 1 This distinction is critical for patient safety and appropriate prescribing.