Veterinary science is making advances in the medical management of canine idiopathic epilepsy, a condition for which there is currently no cure.
A recently published study may help veterinarians decide how best to use phenobarbital and potassium bromide for individual dogs, with at least one new medication showing promise as an alternative to these two drugs.
Phenobarbital vs. Potassium Bromide as Treatment for Epileptic Dogs
A recent study by Dr. Dawn Boothe and colleagues at Auburn University found that phenobarbital is often better tolerated in the first six months of treatment with a higher proportion of dogs having no seizures.
For those dogs that did have episodes, seizures did not last as long.
Both drugs have side effects, including excess hunger and thirst, lethargy and problems with coordination. But phenobarbital has been implicated in liver toxicity when used long term and sometimes damages both red and white blood cells. In an interview with Decoded Science, Dr. Boothe noted that one of the interesting findings from the study was that the incidence of phenobarbital side effects was higher than expected.
She suggested keeping phenobarbital doses below the maximum range. Identifying at risk patients, such as dogs with signs of liver disease, those on other drugs metabolized in the liver, and elderly animals, for closer monitoring may help reduce the incidence of liver toxicity. According to Dr. Boothe, further study is needed to completely understand risk factors for phenobarbital induced liver toxicity.
Epilepsy in Dogs – New Seizure Medications Tested
Several medications are now prescribed as secondary, add-on medication for dogs whose seizures are not controlled by either phenobarbital or potassium bromide. One of the most promising, according to Dr. Boothe, is zonisamide, which can be used as both a sole medication and an add-on with few side effects.
Felbamate offers another sole treatment option, although it is most often used for other types of seizures, rather than for idiopathic epilepsy. Unfortunately, like phenobarbital, felbamate is associated with liver toxicity and abnormal blood cells. Levitiracetam, to date, shows few of the side effects seen with other antiepileptic drugs. This promising secondary treatment for seizures in dogs does, however, require dosing three times a day.
Gabapentin, another three times a day medication used as an add-on to phenobarbital or potassium bromide, appears to be the least effective of the new drugs being tested. Longer term studies will help further evaluate these medications for controlling canine idiopathic epilepsy, while ongoing research into the genetic basis for some idiopathic epilepsy holds promise for reducing the incidence of the condition.
Canine Epilepsy Treatment: The Role of the Placebo Effect
An interesting study found that 79% of the dogs receiving a placebo in three separate clinical trials had decreased seizure activity. While no one would recommend treating canine epilepsy with a placebo, it does indicate the importance of placebo–controlled studies when evaluating seizure medications for dogs. As the newer antiepileptic medications are trialed, placebo-controlled testing needs to be included.
It is important for the owner of dogs suffering from idiopathic epilepsy to understand that, to date, there is no one ‘best’ antiepileptic medication. Owners need to work closely with their veterinarian until their pet’s seizures are eliminated or significantly reduced. Research on a genetic basis for idiopathic epilepsy may aid in reducing the incidence of this condition.
Boothe, DM., Dewey, C., and Carpenter, DM. Comparison of phenobarbital with bromide as a first-choice antiepileptic drug for treatment of epilepsy in dogs. (2012). Journal of the American Veterinary Medical Association. 240 (9).1073-1083. Accessed June 14, 2012.
Hoskins, J. D. New anticonvulsant drugs show promise in dogs, cats. DVM Newsmagazine. Accessed June 14, 2012.
Muñana, K.R., Zhang, D. and Patterson, E.E. Placebo Effect in Canine Epilepsy Trials. (2010). Journal of Veterinary Internal Medicine, 24: 166–170. doi: 10.1111/j.1939-1676.2009.0407.x. Accessed June 14, 2012.