Zonisamide for Treating Canine and Feline Seizures
Zonisamide is an anticonvulsant medication that is unrelated to other anticonvulsants routinely used for treating dogs and cats. Zonisamide can be used together with Phenobarbital and/or potassium bromide for treating seizures. This may be useful in cases where your dog's seizures are not adequately controlled by taking Phenobarbital or potassium bromide alone or combined.
Zonisamide can also be used by itself as opposed to 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 dog.
While Zonisamide appears to be effective in controlling seizures for many dogs and seems to be well-tolerated, many veterinarians are still concerned that we may not know the entire range of side effects possible with the drug because its use has been somewhat limited so far.
Zonisamide levels in the blood can be measured, but there is a lack of agreement between veterinarians regarding whether 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 in Dogs and Cats
As with most anticonvulsant drugs, Zonisamide can cause drowsiness, incoordination and a depressed appetite in dogs. However, there is concern that there may be side effects associated with Zonisamide, of which we are currently unaware because it has had limited usage in dogs compared to many of the other drugs that we use routinely.
Nevertheless, Zonisamide does seem to be relatively safe for dogs.
Zonisamide also appears to be relatively safe in cats based on the what we know so far. Zonisamide has had even more limited use in cats than in dogs, though, and some veterinarians worry that we may not be fully aware of the safety profile and potential side effects that may occur using Zonisamide for cats. (Zonisamide is known to cause birth defects in puppies and kittens and should not be given to pregnant or nursing animals.)
Source: Plumb's Veterinary Drug Handbook, 6th edition, Donald C Plumb