Brain Disease in Dogs: New Anticonvulsant Therapies are Available!

Several new anticonvulsant drugs have been introduced to treat seizure disease in dogs.  TheBrain Disease in Dogs: New Anticonvulsant Therapies are Available! effectiveness of these drugs has not been well documented for any of these drugs.  They are typically used in situations where the more common anticonvulsant drugs, phenobarbital or potassium bromide, are either not effective or well tolerated.  The cost of maintenance anticonvulsant therapy is often a consideration when choosing the proper dose to treat seizure disease in dogs.  The newer anticonvulsant drugs used to treat seizures in dogs are quite expensive compared to the most common drugs used in dogs, phenobarbital and potassium bromide.  However, some of these drugs are now available as generic drugs, making their cost much less.

Felbamate (Felbatol) is a newer anticonvulsant drug used to seizure disease in dogs.

Flebamate has demonstrated effective control of partial (focal) and generalized forms of seizure disease in dogs.  Felbamate appears to be effective both as an add-on drug and as a single agent anticonvulsant drug for dogs with focal and generalized seizures.  One benefit of felbamate is its lack of sedation.  It also has a wide margin of safety in dogs, with little risk of serious side effects at dosages below 300 mg/kg body weight per day.  Dosing is recommended every 8 hours.  It appears to have a wide therapeutic range of between 20-100 mcg/ml in the blood, similar to people.  Due to the wide therapeutic range, low toxicity potential, and high cost of testing felbamate blood levels, routine checking of felbamate blood levels in dogs is of questionable clinical value.  In dogs with pre-existing liver disease, the drug should be avoided due to the potential for liver toxicity.  The risk of liver toxicity would be expected to be greater in dogs receiving phenobarbital concurrently.

Levetiracetam (Keppra) as a newer anticonvulsant drug used to seizure disease in dogs.

Levetiracetam has demonstrated effective control of partial (focal) and generalized forms of seizure disease in dogs.  It is largely used as an add-on anticonvulsant drug with favorable results.  Its mechanism of action is not entirely clear, but it does not appear to affect common neurotransmitter pathways or ion channels the way most other anticonvulsants do.  It is an oral drug that is best dosed every 8 hours.  It appears to have an extremely high margin of safety.  Levetiracetam is not metabolized by the liver and therefore can be used safely in dogs with liver problems.   There is no clear relationship between blood levels (serum drug concentration) and the effectiveness of the drug, there for monitoring blood levels of the drug (therapeutic drug monitoring) is of uncertain benefit.

Zonisamide as a newer anticonvulsant drug used to seizure disease in dogs.

Zonisamide has demonstrated effective control of partial (focal) and generalized forms of seizure disease in dogs.  It is largely used as an add-on anticonvulsant drug with favorable results, but also appears to have effectiveness as a sole anticonvulsant agent.  It is an oral drug that is best dosed every 12 hours.  The drug is primarily metabolized by the liver.  Mild side effects such as transient sedation, ataxia and vomiting have been reported.

Gabapentin as a newer anticonvulsant drug used to seizure disease in dogs.

Gabapentin is occasionally helpful as an anticonvulsant drug to treat seizure disease in dogs that is available in generic form.  It is better used as an add-on drug than as a single agent drug and is more effective for focal seizure disorders than generalized seizure disease in dogs.  The drug is metabolized by the liver, but does not appear to cause liver enzyme elevations, unlike many other anticonvulsant drugs.  Dosing needs to be administered at least every 8 hours, and possible every 6 hours.  This dosing can make it difficult for pet owners to administer on a consistent basis.  Sedation is not a major problem, but does occur.

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Dr Stephen Atwater

Stephen W. Atwater, DVM, MS, Diplomate ACVIM (oncology) is a board-certified veterinary oncology specialist. His professional interests include utilizing emerging therapies for difficult to treat cancers.

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