Zonisamide
Also known as: Zonegran, Excegran
* **Strict Schedule**: Give this medication exactly as prescribed. Missed doses can lead to breakthrough seizures. * **Do Not Stop Abruptly**: Sudden discontinuation can cause severe "rebound" seizures. Always consult your veterinarian before changing the dose. * **Seizure Diary**: Keep a detailed log of any seizure activity (date, time, duration, severity) to help your veterinarian adjust the dose accurately. * **Side Effects**: Mild sleepiness or clumsiness may occur initially but usually improves as your pet adjusts to the medication. Contact your vet if your pet stops eating, vomits, or develops red/dry eyes.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Epilepsy (anecdotal)
- Refractory to phenobarbital
- Epilepsy
- Epilepsy
- Refractory epilepsy (with phenobarbital)
- Monotherapy
- Add-on with phenobarbital
- Initial monotherapy
- Add-on agent
- Epilepsy
- Epilepsy (monotherapy or adjunctive)
How it is given
Possible side effects
- Sedation (usually transient)
- Ataxia
- Inappetence / Anorexia
- Vomiting
- Diarrhea
- Somnolence
- Keratoconjunctivitis sicca (KCS) - theoretical risk due to sulfonamide structure
- Polyarthropathy or blood dyscrasias - theoretical risk due to sulfonamide structure
- Sedation
- Anorexia
- Keratoconjunctivitis sicca (KCS)
- Hepatotoxicity (rare)
- Metabolic acidosis
Cautions & contraindications
- Hypersensitivity to zonisamide
- Hypersensitivity to sulfonamide drugs
- Pregnancy (known teratogen in dogs)
- Hypersensitivity to sulfonamides
- Severe hepatic impairment
- > **Teratogenic Risk**: Zonisamide is a known teratogen in dogs. Doses of 10-30 mg/kg/day have caused ventricular septal defects, cardiomegaly, and valvular/arterial anomalies (threshold plasma level for malformation is 25 mcg/mL). Use in pregnant dogs carries significant risks. * **Sulfonamide Sensitivity**: Because it is a sulfonamide, monitor for idiosyncratic sulfonamide reactions (e.g., KCS, blood dyscrasias), though clinical reports in veterinary patients are currently rare. * Use with caution in nursing animals as it is unknown if it enters maternal milk.
Drug interactions
- Phenobarbital: Increases the clearance of zonisamide. Repeated phenobarbital dosing decreases the bioavailability, peak concentrations, half-life, and AUC of zonisamide. This effect can persist up to 10 weeks after phenobarbital discontinuation. Higher zonisamide doses are typically required.
- Ketoconazole: May inhibit the hepatic metabolism of zonisamide, potentially increasing serum concentrations.
Frequently asked questions
What is Zonisamide used for in pets?
* **Strict Schedule**: Give this medication exactly as prescribed. Missed doses can lead to breakthrough seizures. * **Do Not Stop Abruptly**: Sudden discontinuation can cause severe "rebound" seizures. Always consult your veterinarian before changing the dose. * **Seizure Diary**: Keep a detailed log of any seizure activity (date, time, duration, severity) to help your veterinarian adjust the dose accurately. * **Side Effects**: Mild sleepiness or clumsiness may occur initially but usually improves as your pet adjusts to the medication. Contact your vet if your pet stops eating, vomits, or develops red/dry eyes.
Is Zonisamide safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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