Antiepileptic drug therapy

Successful treatment of seizure disorders in small animals requires proper patient assessment, understanding the principles of antiepileptic drug (AED) therapy, designing a strategy for pharmacotherapy, and plans for emergency treatment. Several levels of assessment are needed in managing an epileptic patient to include the diagnosis, effectiveness of therapy, and health-related quality of life assessments. Three levels of diagnosis are important in determining the appropriate AED therapy: 1) confirmation that an epileptic seizure has occurred, and if so, the seizure type(s) manifested; 2) diagnosis of the seizure etiology; and 3) determination of an epileptic syndrome. Monotherapy is the initial goal of treating any cat or dog with epilepsy to reduce possible drug-drug interactions and adverse effects. Unfortunately, many of the AEDs useful in people cannot be prescribed to small animals either due to inappropriate pharmacokinetics (too rapid of an elimination), and potential hepatotoxicity. Thus, the most commonly used AEDs in veterinary medicine are from the same mechanistic category, that of enhancing inhibition of the brain. Antiepileptic drugs can be classified into three broad mechanistic categories: 1) enhancement of inhibitory processes via facilitated action of gamma amino-butyric acid (GABA); 2) reduction of excitatory transmission; and 3) modulation of membrane cation conductance. Pharmacotherapy strategies should be designed based on the decision when to start treatment, choice of the appropriate AED, and proper AED monitoring and adjustment. Information is presented for the current AEDs of choice, phenobarbital and bromide. Additional guidelines are provided for administration of newer AEDs, felbamate and gabapentin. All owners should be aware that emergency therapy may be necessary if recurrent or severe seizures occur in their pet. A rapid, reliable protocol is presented for the emergency management of seizuring cats and dogs in the hospital and at home. Home treatment with per rectal administration of diazepam in the dog has proven to be an effective means of reducing seizure frequency and owner anxiety. Treating each animal as an individual, applying the philosophy that seizure prevention is better than intervention, and consulting specialists to help formulate or revise treatment plans will lead to improved success in treating seizure disorders in the cat and dog.