As sole drug therapy
There are a number of reports in human medical literature supporting the use of some of these new anticonvulsant drugs as
sole therapy. Because they have minimal side effects, they may offer an advantage over more standard drugs used in dogs. And,
as the price decreases for generic versions, there will be more opportunities to use these newer agents as standard therapy,
especially in small-breed dogs.
Anecdotally, felbamate can be used as a sole anticonvulsant drug. In most cases, it is used to avoid the side effects of phenobarbital
or potassium bromide. Such cases include the management of disorders in which the underlying disease and its treatment may
result in worsening clinical signs with the addition of standard anticonvulsant drugs (e.g., obtunded brain tumor and GME
dogs receiving prednisone).
In addition, dogs with suspected idiopathic epilepsy have been treated with zonisamide as a sole anticonvulsant drug. It appears
to perform well as a sole anticonvulsant drug for canine idiopathic epilepsy.
New feline anticonvulsant drugs
Until recently, the only anticonvulsant drug known to be safe and effective for feline use was phenobarbital. The use of gabapentin
for seizures in cats remains anecdotal, with unproven efficacy. Due to the length of time that such anecdotal use has been
discussed in the veterinary literature (with no reports of serious side effects), and the known safety of the drug in other
species (i.e., humans, dogs), it is likely to be a safe drug in cats.
Levitiracetam has been used as an add-on (to phenobarbital) oral anticonvulsant drug in a few cats with suspected refractory
idiopathic epilepsy. It was found to be an effective add-on anticonvulsant, and serum levitiracetam levels are maintained
within the therapeutic range reported for people (5-45 ug/mL) using a 20 mg/kg every 8 hours dosing regimen. Side effects
are limited to transient (one to two weeks) lethargy and inappetence; these resolved without adjusting drug dosage.
Levitiracetam can be used as second-line anticonvulsant drug choice for cats poorly controlled with phenobarbital alone.
Emergency seizure management
The current standard of care for treating dogs with cluster seizures or status epilepticus is to administer highly sedative
drugs to halt seizure activity. As diazepam often fails in these animals, the induction of a light plane of anesthesia using
barbiturates or propofol often is required.
In addition to posing some risk, it may be difficult or impossible to add additional maintenance anticonvulsant drugs to the
treatment protocol during this time period.
Both intravenous levitiracetam and intra-rectal zonisamide hold potential as useful emergency anticonvulsant treatment options
A commercial form of intravenous levetiracetam was recently introduced. A single-dose pharmacokinetic study with this drug
formulation in normal dogs, using an intravenous bolus dose of 60 mg/kg over two minutes, showed no apparent side effects
and all dogs reached and maintained plasma levitiracetam concentrations within or exceeding the therapeutic range reported
for humans for the entire eight-hour evaluation period.
A prospective clinical evaluation of intravenous levitiracetam use in dogs with cluster seizures and status epilepticus is