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First-line anticonvulsant therapy
Anticonvulsants are a varied group of drugs used to manage epileptic seizures. Their broad spectrum action on various neurotransmitters, receptors and ion channels also means that they may have efficacy for other pathological conditions, such as neuropathic pain and movement disorders. Anticonvulsants are often referred to as antiepileptic drugs (AEDs), but this is somewhat inappropriate as the mode of action of most AEDs is to suppress seizures, not epileptogenesis. In other words, unlike the majority of other drugs prescribed in veterinary medicine, they do not modify the disease course, provide prophylaxis or offer a true pharmacotherapeutic cure, but merely suppress signs of the disease. In this article, the drugs used for first-line therapy are discussed together with common pitfalls and complications.
The author's approach to the first-line management of epilepsy in dogs and cats is illustrated in Figs 1 and 2 , respectively. First-line AED therapy in dogs is phenobarbital or potassium bromide monotherapy. There are no licensed AEDs in cats and the author's first-line drug is again phenobarbital. Phenobarbital and bromide have a synergistic effect and can be used in combination therapy in dogs where monotherapy is ineffective.
Bromide
Bromide is an old drug and its use in managing epilepsy was first described in 1857 (Anon). Veterinary preparations were readily available in the early 20th century. For example, the 1912 Parke Davis veterinary products catalogue listed a 'Medicinal Elixir of Bromide and Chloral Compound' containing chloral hydrate, potassium bromide, extract of hyoscyamus and Indian cannabis. Texts of this era recommended bromide for treating seizures, in particular those associated with distemper encephalitis ( Fig 3 ). However, as in human medicine, the use of bromide for canine epilepsy diminished after phenobarbital and phenytoin became available. Resurgence of the use of potassium bromide in veterinary medicine occurred in the early 1990s and authorised veterinary products are available in the UK. Bromide has also recently regained popularity in human medicine for the treatment of intractable childhood epilepsy. One advantage of bromide is that it does not require liver metabolism, making it one of the few 'liver-safe' AEDs. Another advantage is that it may be dosed once daily; its long half-life means that variation in dosing times or even missed doses may not affect...