Although, in the past potassium bromide was only used as a second line anti-convulsant, when Phenobarbital alone did not control seizures, today it is becoming an alternate choice of first line medications. Potassium bromide can be used alone or in addition to Phenobarbital to control seizures. The addition of bromide improves seizure control in about 70 to 80% of dogs with idiopathic epilepsy refractory to Phenobarbital.
Bromide is the active component in potassium bromide and can be mixed with either potassium or sodium when used as an anti-convulsant. Anti-seizure activity is thought to be the result of bromide's generalized depressant effects on neuronal excitability and activity. Bromide ions compete with chloride transport across cell membranes resulting in membrane hyperpolarization (possessing a highly negative charge), thereby raising seizure threshold and limiting the spread of epileptic discharges.
Potassium bromide is very stable and does not need refrigeration, unless it is flavored with an ingredient that is perishable. Please ask your pharmacist how to store your dog's bromide.
Potassium Bromide Facts:
Mean Elimination Half-Life: 24 to 46 days
Time to Reach Steady State Concentrations: 3 to 4 months
Target Serum Concentration: 2 to 3 mg/ml when used alone and 1 to 2 mg/ml when used in conjunction with Phenobarbital .
Adverse Effects: The common side effects of Potassium Bromide are excessive hunger, excessive thirst, excessive urination, lethargy and ataxia (hind end weakness). It is not uncommon for some patients to demonstrate depression or sedation when first starting on Potassium Bromide. These effects are usually transient and resolve as the patient acclimates to the medication. If these side effects do not resolve, or if they are extremely pronounced, talk to your veterinarian.
Please note that some dogs become extremely hungry when they first start Kbr. Many dogs will pace, whine, bark, try to steal food or even eat inappropriate items. For more information please see the section on abnormal behavior.
Potassium can be very irritating to the stomach and some dogs experience gastric upsets from it. For these dogs, splitting the daily dose in two and always giving it with food may help. For dogs who can't tolerate potassium even when the dose is divided and given with food, sodium bromide may be an alternative. Sodium bromide and potassium bromide are equally effective at controlling seizures.
A less common, but more serious potential side effect of Potassium Bromide is Pancreatitis. A retrospective study suggests that potassium bromide may cause severe pancreatitis in dogs. This reaction does not appear to be dose dependent and may happen shortly after starting on bromide. The symptoms of pancreatitis are wide ranging and varying in severity. The most common symptoms are poor appetite, vomiting, depression, dehydration, abdominal pain, diarrhea and fever. If your dog exhibits any of these symptoms, please call your veterinarian immediately.
In addition to pancreatitis, there is growing concern that high serum levels (usually over 3 mg/ml but there is a wide variance) of potassium bromide may increase the risk of megaesophagus. There are no studies proving an association but many neurologists have commented that they have seen an increased incidence of this condition in their patients. The symptoms of megaesophgus include cough, regurgitation (passive expulsion of food and water) nasal discharge and fever.
Although the risk of either pancreatitis or megaesophagus appear to be very small, they are both life threatening conditions. It is very important to contact your vet immediately if your dog shows any of the symptoms of either disorder. Both are usually successfully treated when they are caught early.
Monitoring: There are many monitoring protocols but in general, potassium bromide levels should be checked approximately 30 days after initiating therapy to determine the blood serum levels.
Once you have obtained seizure control, your vet will probably want to monitor blood serum concentrations every 6 months to be sure that the serum level has not drifted out of range.
Cautions and Warnings: Potassium bromide should be used cautiously in dogs with renal insufficiency as these dogs will not clear bromide efficiently and less bromide is required to maintain target serum levels.
Do not change your dog's diet without consulting with your vet after you have started potassium bromide therapy. Bromide and chloride compete for absorption by the kidneys and bromide will be sacrificed for chloride. Changing the chloride content in your dog's diet may cause bromide serum concentrations to drop below therapeutic range causing seizures or it may cause bromide levels to rise causing bromide toxicity. (note: salt is one form of chloride but it isn't the only type).
Loading Doses: Your vet may feel that it is necessary to do a loading dose of bromide in order to decrease the amount of time it takes to be effective. Typically loading doses are given when there is a need to eliminate Phenobarbital quickly or when Phenobarbital alone is not providing control for a dog with severe seizures. Although loading doses will control seizures faster, they also tend to cause more side effects initially. Ataxia (or hind end weakness) is probably the most pronounced but ataxia and other side effects should resolve in 2 to 3 weeks.
Discontinuing Therapy: Never discontinue therapy or alter the dose of this medication, without first consulting with your veterinarian.
Berendt, M, Clinical
Neurology in Small Animals-Localization, Diagnosis and Treatment
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Last Updated August 2009