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Zonisamide

Prescription
Sulfonamide antiepileptic
Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
2 available
Interactions
1 documented
Formulations
3

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
PO
Frequency
BID
Max dose
500 mg/dose; 1000 mg/day
Duration: Long-term
🐈

Cat

Epilepsy (adjunctive)
Dose
5–10 mg/kg
Route
PO
Frequency
SID to BID
Max dose
100 mg/dose; 200 mg/day
Duration: Long-term

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)

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.

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.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
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 →