Zonisamide

Zonisamide In Dogs & Cats: Uses, Dosage and Side Effects

Overview

• Zonisamide’s exact mechanism for treating epilepsy is uncertain.
• It may work by blocking the repetitive firing of sodium channels.
• It could also inhibit calcium channels.
• Additionally, it may modulate the activity of neurotransmitters like GABA and glutamate

Uses of Zonisamide

• Zonisamide is a sulphonamide anticonvulsant, which is usually used in dogs and cats as an adjunctive therapy in animals refractory to standard anticonvulsant therapy (in dogs, phenobarbital, imepitoin and potassium bromide).
• It is well absorbed with a half-life of 15–17 hours in the dog.
• The drug is metabolized by the liver and then mostly excreted by the kidneys.

Dose of Zonisamide in Dogs and Cats

Dogs:

• Starting dose of 5–10 mg/kg p.o. q12h.

Cats:

• Starting dose of 5–10 mg/kg p.o. q24h is suggested.

Side Effects of Zonisamide in Dogs and Cats

• Ataxia, sedation, vomiting, and anorexia have been observed in some dogs and cats.
• In dogs, experimental doses as high as 75 mg/kg administered once daily or divided into twice daily doses have been used for up to 52 weeks.
• Initially, weight loss was noted in dogs receiving these doses.
• Over the long term, minor liver and blood-related changes were observed.

Contraindications of Zonisamide in Dogs and Cats

• Avoid administering zonisamide to patients with severe liver problems.
• Refrain from using it in pregnant animals due to demonstrated toxicity in experimental studies.
• Do not abruptly stop treatment with zonisamide.

Some Notes:

• Phenobarbital increases clearance of zonisamide up to 10 weeks after phenobarbital discontinuation.
• If using as an adjunctive to phenobarbital consider using doses at the higher end of the dose range.