Zonisamide


Concise Prescribing Info
Indications/Uses
Partial seizures.
Dosage/Direction for Use
Adult : PO Adjunctive therapy: Initial: 50 mg/day in 2 divided doses increase to 100 mg/day after 1 wk, then may further increase at wkly intervals in increments of up to 100 mg. Maintenance: 300-500 mg/day. Monotherapy: In newly diagnosed patients: Initial: 100 mg once daily, increase to 200 mg once daily after 2 wk. May further increase by increments of 100 mg at intervals of at least 2 wk. Maintenance: 300-500 mg/day.
Dosage Details
Oral
Adjunct in partial seizures
Adult: Initially, 50 mg daily in 2 divided doses, increase to 100 mg daily after 1 wk. Thereafter, may further increase dose at wkly intervals in increments of up to 100 mg. Usual maintenance dose: 300-500 mg daily, some patients may respond to lower doses.
Child: > 6 yr Initially, 1 mg/kg once daily for 1 wk, may increase by increments of 1 mg/kg at wkly interval. Usual maintenance dose: 20-55 kg: 6-8 mg/kg once daily; >55 kg: 300-500 mg once daily, some may respond to lower dose.

Oral
Monotherapy for partial seizures with or without secondary generalisation
Adult: In patients w/ newly diagnosed epilepsy: Initially, 100 mg once daily, increase to 200 mg once daily after 2 wk. May further increase by increments of 100 mg at intervals of at least 2 wk. Usual maintenance dose: 300 mg once daily, up to 500 mg daily.
Renal Impairment
GFR ≥50 mL/min: Slower dosage titration may be needed. GFR <50 mL/min: Not recommended.
Hepatic Impairment
Mild to moderate: Slower dosage titration may be needed. Severe: Not recommended.
Administration
May be taken with or without food.
Contraindications
History of hypersensitivity to sulfonamides.
Special Precautions
Patient at risk of nephrolithiasis. Avoid abrupt withdrawal. Renal or hepatic impairment. Childn. Pregnancy and lactation.
Adverse Reactions
Abdominal pain, anorexia, diarrhoea, nausea, dyspepsia, constipation, dry mouth, taste perversion, headache, dizziness, ataxia, nystagmus, paraesthesia, confusion, difficulty concentrating, impaired memory, speech abnormalities, agitation, irritability, depression, insomnia, anxiety, nervousness, schizophrenic behaviour, somnolence, fatigue, flu-like syndrome, ecchymosis, rhinitis, wt loss, rash, diplopia.
Potentially Fatal: Severe hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme; fulminant hepatic necrosis, agranulocytosis, aplastic anaemia and other blood dyscrasias.
Patient Counseling Information
Increase fluid intake (i.e. 6-8 glasses of water/day) to reduce risk of renal stone. This drug may cause drowsiness or difficulty w/ concentration, if affected, do not drive or operate machinery.
MonitoringParameters
Monitor metabolic profile specifically BUN, serum creatinine; serum bicarbonate, body temp, suicidality, decreased sweating.
Overdosage
Symptoms: Somnolence, nausea, gastritis, nystagmus, myoclonus, coma, bradycardia, reduced renal function, hypotension and respiratory depression. Management: Supportive treatment. Induce emesis or perform gastric lavage to reduce drug absorption.
Drug Interactions
Reduced plasma concentration w/ phenytoin, phenobarbital, carbamazepine. Increased risk of metabolic acidosis w/ carbonic anhydrase inhibitors (e.g. acetazolamide).
Action
Description: Zonisamide is a benzisoxazole derivative anticonvulsant containing sulfonamide. It may act on voltage sensitive Na and Ca channels, thereby affecting neuronal firing, hence reducing the spread of seizure discharges. It may modulate GABA-mediated neuronal inhibition.
Pharmacokinetics:
Absorption: Almost completely absorbed from GI tract. Bioavailability: Approx 100%. Time to peak plasma concentration: W/in 2-6 hr.
Distribution: Widely distributed into body tissues. Crosses placenta and distributed into breast milk. Plasma protein binding: 40-50%; extensively bound to erythrocytes.
Metabolism: Undergoes acetylation to N-acetylzonisamide and subsequent reduction mediated by CYP3A4 isoenzyme to 2-sulfamoylacetylphenol (SMAP).
Excretion: Via urine (approx 15-30% as unchanged drug, 15% as N-acetylzonisamide, 50% as the glucuronide of SMAP). Plasma elimination half-life: Approx 63 hr.
Chemical Structure

Chemical Structure Image
Zonisamide

Source: National Center for Biotechnology Information. PubChem Database. Zonisamide, CID=5734, https://pubchem.ncbi.nlm.nih.gov/compound/Zonisamide (accessed on Jan. 24, 2020)

Storage
Store between 15-30˚C. Protect from light and moisture.
MIMS Class
ATC Classification
N03AX15 - zonisamide ; Belongs to the class of other antiepileptics.
References
Anon. Zonisamide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 15/06/2016.

Buckingham R (ed). Zonisamide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 15/06/2016.

Joint Formulary Committee. Zonisamide. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com/. Accessed 15/06/2016.

McEvoy GK, Snow EK, Miller J et al (eds). Zonisamide. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 15/06/2016.

Zonisamide Capsule (Apotex Corp). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 15/06/2016.

Disclaimer: This information is independently developed by MIMS based on Zonisamide from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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