Using Zonisamide for Treating Seizures in Dogs

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If your dog or cat has been diagnosed with epilepsy or another seizure disorder, the veterinarian may prescribe an anticonvulsant. However, if you find your pet is not reacting well to these drugs, there is another option—a medication called Zonisamide. 

Zonisamide is an anticonvulsant medication that is unrelated to the other anticonvulsants routinely used for treating dogs. Zonisamide can be used alone or in combination with phenobarbital and/or potassium bromide for treating seizures. This may be useful in cases where your pet's seizures are not adequately controlled by taking traditional anti-seizure medications either alone or combined. It may also be a good alternative for animals that are allergic to or have serious side effects from other anti-seizure medications.

Ways to Take Zonisamide

Zonisamide can be used by itself or combined with other anticonvulsant medications. For dogs that cannot tolerate phenobarbital or potassium bromide, Zonisamide may be a viable option. It may also be an option for dog owners who do not want to risk the side effects of phenobarbital or potassium bromide for their pets. Side effects of phenobarbital or potassium bromide for dogs may include sedation, restlessness, loss of coordination, changes in thirst and appetite, or increased urination, among many other issues.

Zonisamide levels in the blood can be measured, but there is a lack of agreement among veterinarians regarding whether the measurement of blood levels is needed. Some veterinarians believe that measuring is important to evaluate whether the dosage is adequate and is not approaching toxic levels. Others prefer to rely on clinical signs and monitoring of seizure activity to determine the efficacy of the medication dosage for the pet.

Side Effects of Zonisamide

While Zonisamide appears to be relatively safe for dogs, is effective in controlling seizures, and is well-tolerated, many veterinarians are concerned because long-term studies have yet to show safety and effectiveness. As with most anticonvulsant drugs, Zonisamide can cause drowsiness, incoordination (loss of muscle control), and a depressed appetite in dogs. It can also cause vomiting, diarrhea, anorexia, and in rare cases, skin reactions, hyperthermia, and blood disorders.


Zonisamide is known to cause birth defects in puppies and should not be given to pregnant or nursing animals. It should also not be given to animals that are hypersensitive to sulfa drugs.

Administration and Dosage of Zonisamide

Your veterinarian will determine the best method of administration and dosage for your dog, taking into consideration the best outcome and your pet's safety. The most common form of this drug is in a sugar-coated tablet. The average dosage for a dog with epilepsy is 8 to 12 mg/kg administered by mouth every eight to 12 hours.


Plumb, Donald C. Plumb's Veterinary Drug Handbook, 6th edition. John Wiley and Sons: USA. 2016.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.