Home/Medicines/Zonisamide

Zonisamide

Prescription

Sulfonamide antiepileptic

Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

2 available

Interactions

1 documented

Formulations

Mechanism of action

Blocks voltage-gated sodium and T-type calcium channels; also modulates GABAergic and glutamatergic neurotransmission

At a glance

Class

Sulfonamide antiepileptic

Schedule

Prescription

Storage

Store below 25°C, protect from light and moisture

Dosing

🐕

Dog

Epilepsy (adjunctive or monotherapy)

Dose

3–10 mg/kg

Route

Frequency

BID

Max dose

500 mg/dose; 1000 mg/day

Duration: Long-term

🐈

Cat

Epilepsy (adjunctive)

Dose

5–10 mg/kg

Route

Frequency

SID to BID

Max dose

100 mg/dose; 200 mg/day

Duration: Long-term

Educational reference only

This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Formulations

💊

Capsule — 3

Strength

25mg

Available in India

Strength

50mg

Available in India

Strength

100mg

Available in India

Storage

Store below 25°C, protect from light and moisture

Safety

Absolute contraindications — do not use

Sulfonamide hypersensitivity

Use with caution

Hepatic or renal impairment
Dose adjustment may be needed

Adverse effects

Common

Sedation

Ataxia

Inappetence

Vomiting

Serious

Hepatotoxicity

Renal tubular acidosis

KCS (cats)

Monitoring parameters

Seizure diaryHepatic enzymesBUN/CreatinineSchirmer tear test (cats)

Educational reference only

Interactions

Moderate — 1

Phenobarbital

moderate

Phenobarbital induces CYP3A4, increasing zonisamide clearance and reducing serum levels

Management: Monitor zonisamide levels. May need higher doses when used concurrently with phenobarbital.

Educational reference only

Brands

International

Zonegran

Eisai

India

Zonisep

Sun Pharma

FAQs

Frequently asked questions

›What is Zonisamide?

Zonisamide is a sulfonamide antiepileptic used in pets. Blocks voltage-gated sodium and T-type calcium channels; also modulates GABAergic and glutamatergic neurotransmission

›What is Zonisamide used for in pets?

Zonisamide is used in veterinary medicine for: Epilepsy (adjunctive or monotherapy); Epilepsy (adjunctive).

›What is the Zonisamide dose for dogs?

For dogs, Zonisamide is typically dosed as follows — Epilepsy (adjunctive or monotherapy): 3–10 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Zonisamide dose for cats?

For cats, Zonisamide is typically dosed as follows — Epilepsy (adjunctive): 5–10 mg/kg PO SID to BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What are the side effects of Zonisamide?

Common: Sedation, Ataxia, Inappetence, Vomiting. Serious (call your vet immediately): Hepatotoxicity, Renal tubular acidosis, KCS (cats).

›Does Zonisamide need a prescription?

Yes. Zonisamide is a prescription medication and should only be administered under veterinary supervision.

›When should Zonisamide not be used?

Do not use Zonisamide if: Sulfonamide hypersensitivity.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database