• Neurologic Diseases
• Companion Animals
• Veterinary Medicine

• Neurologic Diseases
• Companion Animals

It is important to accurately diagnose and treat seizure disorders because prolonged seizure activity can result in brain damage. Patricia Dowling, DVM, MSc, Western College of Veterinary Medicine, Saskatoon, Saskatchewan, Canada, gave a presentation regarding best practices in treating dogs with epilepsy. Pharmacotherapy is typically recommended in dogs having seizures more than once a month, those having > 1 seizure per day, or those presenting with status epilepticus. Phenobarbital and potassium bromide (KBr) remain the most effective antiepileptic drugs in dogs. Characteristics of both drugs are summarized in Table 1. Dr. Dowling emphasized that when a treatment strategy is devised, the expectations of the owner must be considered. Owners must understand that their dogs will continue to have seizures while on medication and that the objective is to decrease seizure frequency, duration, and severity.

Phenobarbital is often the first-line treatment of seizures in dogs, with KBr added if needed. A typical slow-induction dosing regimen is phenobarbital, 2 to 4 mg/kg/d, divided every 8 or 12 hours. If necessary, the phenobarbital dose may be increased to 18 to 20 mg/kg/d divided every 8 or 12 hours. Phenobarbital is primarily metabolized by the liver and induces microsomal P-450 enzymes in dogs within days of starting the drug. This induction can affect concurrently administered drugs. If treatment needs to be stopped, phenobarbital should be tapered by decreasing the dose by 10% to 25% every 2 weeks. However, in cases where the dog has serious adverse effects, the drug must be stopped abruptly. Given the long half-life of phenobarbital, dogs generally do not experience withdrawal symptoms or breakthrough seizures.

KBr is used as an add-on to phenobarbital or as a monotherapy alternative in dogs that cannot tolerate phenobarbital. KBr is renally eliminated and does not undergo hepatic metabolism, so it is useful in dogs with liver disease. The typical starting dose for dogs on a normal commercial dog food diet is 20 mg/kg divided every 12 hours in food to reduce nausea. When KBr is given as monotherapy, the starting dose is 40 to 50 mg/kg/d, although some dogs may require higher doses to achieve seizure control. In dogs with renal insufficiency, half the recommended dose of KBr should be administered, and drug concentrations should be frequently checked.

KBr doses of 50 to 80 mg/kg/d may be needed in dogs on a high-salt diet to maintain adequate serum concentrations. Bromide and chloride compete for renal tubular reabsorption, so the bromide elimination rate is greater in dogs with high chloride intake. The chloride content of commercial dry dog food varies from 0.45% to 1.09%, and prescription diets may be even higher. Owners should therefore be cautioned to not change their dogs' diets while on KBr therapy and to avoid giving salty treats. Swimming in the ocean has also been associated with breakthrough seizures in some KBr-treated dogs.

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