This article is from the Canine Epilepsy FAQ, by Alicia Wiersma-Aylward with numerous contributions by others.
Medical treatment is generally advised for animals who have one or
more seizures per month. Animals who have cluster seizures or go into
status epilepticus may be treated even though the rate of incidence is
greater than once per month. Successful drug therapy depends upon the
owner's dedication to delivering the drug exactly as prescribed, with
absolutely NO changes in the dose or type of medication without
veterinary consultation. Haphazard drug administration or abrupt
changes in medication is worse than no treatment at all, and may cause
William Thomas, DVM, MS feels it important to remember that the goal
of treatment is to decrease the frequency and severity of seizures and
avoid unacceptable side effects. It may not be possible to stop the
seizures altogether. A number of drugs and some alternative therapies
may be used to control epilepsy. Phenobarbitol and primidone are the
most widely used anticonvulsant drugs, but others have their place in
treatment as well.
Phenobarbitol is one of the most commonly prescribed drugs. Frey
reports that while dogs rapidly develop tolerance to the sedative and
hypnotic effects of phenobarbitol, at high concentrations tolerance
may be lost and persistent depressive side effects may appear. Dogs
may eat or drink more than their usual amounts. Liver function can be
impaired. When use of the drug is terminated, signs of physical
dependence (tremors, incoordination, restlessness, seizures) may
develop. There is danger of triggering status epilepticus during
withdrawal. To avoid this, dosages should be gradually reduced in
small steps over a prolonged period.
Primidone's side effects include sedation when treatment is initiated,
and eating or drinking more than usual. High concentrations of liver
enzymes have been reported with prolonged treatment at high dosages.
Diazepam (Valium) is used for treatment of status epilepticus.
Phenytoin (Dilantin), carbamazine, and valproic acid are not currently
recommended for use.
Potassium bromide (KBr) is gaining new recognition for use in
refractory (difficult to control) canine epilepsy, though used to
treat human epileptics as early as 1857. It is the anticonvulsant of
choice for dogs with liver disease. Sodium bromide is preferred for
dogs with kidney problems. Combining potassium bromide or sodium
bromide and phenobarbitol may be useful for patients who do not
respond well to phenobarbital or primidone alone.
One recent study (Pearce) reported that 10 dogs who had uncontrolled
seizures with phenobarbitol alone had improved control with the
addition of potassium bromide to their drug regimen. The severity of
the seizures and the tendency to cluster were significantly decreased.
An earlier study by Professor Dorothea Schwartz-Porsche
(Sisson/LeCouteur) reported that 5 of 9 epileptics uncontrolled by
phenobarbitol responded to the addition of potassium bromide to either
phenobarbitol or primidone. Podell and Fenner reported that bromide
therapy improved seizure control in 83% of dogs previously unimproved
by phenobarbitol; 26% of the 83% dogs became totally seizure free.
Bromide is not approved for use in dogs, nor is it commercially
available at this time. Veterinarians can obtain it from chemical
supply houses as an American Chemical Society reagent, which dissolves
in water and is added to the dog's food. Dog owners are asked to sign
release forms and are advised to handle the drug with gloves. Thomas
notes that some custom pharmacies will now formulate bromide in
capsules or suspension so the veterinarian doesn't have to.
Side effects of bromide toxicity (bromism) can include incoordination,
depression, muscle pain, and stupor. There are no dermatologic or
gastrointestinal signs as seen in humans taking KBr.