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Author: Admin | 2025-04-28
The decision to start maintenance anticonvulsant or antiepileptic therapy should be based on the frequency and severity of the seizures, the age of onset, the likely cause(s) of the seizures, and the results of diagnostic testing. In general, a maintenance antiepileptic drug (AED) should be considered in animals that have had more than one or two seizures within a 6-mo period (assuming these seizures were not caused by repeated toxin exposure) or in animals that have had more than one seizure of unknown cause on any particular day. A maintenance AED should also be considered if the first seizure episode is protracted or severe, or during an episode of status epilepticus (as a followup to emergency treatment, see Antiepileptic Drugs Used to Stop Ongoing Seizure Activity).Treatment should begin with a single drug at the minimal required level for effect. Owners should keep a calendar to document the frequency and pattern of seizures as a guide for treatment strategy. This calendar, in conjunction with serum AED levels, can be used as a guide for dosage and drug treatment changes. If seizure control is unsatisfactory, the drug level should be checked. If the level is not within the middle of the therapeutic range, the dose should be increased before adding or switching to a new drug. Doses may be doubled in early stages and increased by 25%–50% in later stages. Monotherapy is preferred, but if the drug level is well into the middle or high therapeutic range, it may be necessary to consider the addition of another AED. To discontinue any AED, except bromide, the dose of the drug should be tapered gradually over a few weeks to avoid precipitating a seizure. Tapering phenobarbital is crucial, because it is addictive and can result in withdrawal seizures if stopped abruptly.In dogs, phenobarbital and bromide are considered first-line maintenance AEDs, but levetiracetam and zonisamide are often used as well. In cats, phenobarbital is the usual first choice, but levetiracetam and zonisamide are becoming more acceptable; diazepam is an alternative choice. In ruminants, phenobarbital is the first choice; in horses, both bromide and phenobarbital have been used.Phenobarbital:Phenobarbital has a long record of safety, efficacy, low cost, and convenience in regard to monitoring serum concentrations. For longterm maintenance in cats and dogs, phenobarbital may be given at 2–4 mg/kg/day, PO, bid. In all species, it takes ~2 wk to approach a steady-state plasma concentration, because oral
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