Following the recommendations of the International Veterinary Epilepsy Task Force I suggest starting anticonvulsive drugs if a patient meets one or more of the following criteria:
Two or more seizures within 6 months
History of status epilepticus (one seizure longer than 5 min)
History of cluster seizures (cluster seizures meet the definition in the first point above)
Post ictal signs are severe (ex: aggression) or lasting longer than 24 hours.
Seizure frequency or duration is progressing in the last 3 interictal periods. (ex: 12 months apart, then 8 months then 6 months)
Medications are selected based on the metabolic status of the patient, seizure pattern and client constraints (administration frequency, cost, bias). Phenobarbital and bromide are considered first line treatments by the IVETF and are recommended for most forms of seizures in dogs. Phenobarbital could be considered a first line drug for cats as well (Bromide is a big NO-NO for cats). The level of evidence available to make these recommendations is, at the time of writing, more complete than for the other anticonvulsant drugs. I use the following table to as a guide for starting or changing anticonvulsant drugs; hopefully you find it useful also. Remember that these are guidelines and many animals need manipulation of their seizure control life-long.
Table 1: Indications and limitations of phenobarbital, bromide, levetiracetam, zonisamide and gabapentin as first line anticonvulsant therapy.
PhenobarbitalBromideLevetiracetamZonisamideGabapentinIndication (Dog)Generalized tonic, clonic seizuresFocal or cluster seizuresReactive seizuresGeneralized seizuresInfrequent statusIndication (cat)Generalized, focalnot recommendedReactive seizures, orofacial seizuresLimited data. Consider for generalized?Very little data. Consider as last choice.limitationsAnimals with hepatic disease should not use this drug.Give with care for dogs with renal failure, or renal tubular acidosis (or with zonisamide)Chronic administration may result in honeymoon effectDo not use in cats or dogs with known sulfa hypersensitivity, or liver diseaseNone known
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