Although potassium bromide (KBr) is the most commonly used form, sodium bromide (NaBr) can be used interchangeably with equivalent safety and efficacy.

KBr and NaBr are safe and effective drugs for controlling seizures in dogs, but are not approved drugs (available for investigational use only). Pet owners should be informed of this before Br is prescribed.

Br competes with chloride for trans-port across the neuronal cell membrane, causing hyperpolarization of the cell membrane and thus raising the seizure threshold. Br is absorbed orally and is eliminated by the kidneys. The half-life is approximately 24 days (dog) and 10 days (cat).

Br is indicated for use in combination with Phb in dogs in which seizures are not well controlled with Phb alone. Br also may be used as the sole anticonvulsant drug in dogs when Phb is contraindicated because of its potential hepatotoxic effects. Br is currently being evaluated for use in cats.

Common adverse effects seen with Br or Phb + Br administration include ataxia, transient sedation, polyuria/polydipsia, and polyphagia. Br can cause gastrointestinal upsets. Dividing the daily dose and administering it with food may help to avoid GI side effects. Br should be used with caution in dogs with renal insufficiency, and safety during pregnancy and lactation has not been established.

Br toxicity is uncommon, although it may occur in dogs with renal insufficiency or those on a high dose of Br. Signs of Br toxicity include ataxia, sedation or stupor, and muscle spasm. Reducing the dose by 10% to 25% is usually adequate to resolve clinical signs. If the dog is stuporous because of acute overdose, gastric lavage should be performed; however, this will remove Br only from the stomach. Diuresis with 0.9% sodium chloride will help lower serum Br levels.

Diuretics increase Br excretion and lower serum Br levels. Diets high in salt or chloride will increase Br elimination and result in poor seizure control.

Br and chloride compete for renal tubular reabsorption; increased dietary chloride will cause increased urinary excretion of Br.

The recommended daily maintenance dose of Br is 30 to 40 mg/kg orally; the pharmacokinetics of rectal and parenteral administration in dogs are currently under investigation. A loading dose of 450 to 600 mg/kg, usually divided over 5 days, can be used initially if rapid seizure control is desired. During these 5 days, it is also important to give the maintenance dose; thus, a typical loading protocol would be 120 mg/kg/day plus 35 mg/kg/day for 5 days. Serum Br levels are measured within the first few days after completion of the loading dose. Side effects may be more likely during these 5 days. Weaning from Phb (if required) should be done after 2 to 3 months of Br maintenance therapy or after 1 to 2 days of the Br loading dose.

Therapeutic drug monitoring is essential and should be performed after loading and 2 to 3 months of maintenance therapy, loading, or any change in dosage. Even when the patient is doing well, serum Br levels should be checked every 6 months.

Therapeutic serum levels for most dogs are 1 to 3 mg/mL but may vary depending on the animal’s tolerance. The timing of blood collection for determining Br concentration in relation to administration of the medication is unimportant, because of the long half-life of Br. Use of SST for blood collection should be avoided as it may falsely decrease Br concentration.

Br is available in powder form from any chemical supply company (request medicinal or American Chemical Society [ACS] grade). Many pharmacists compound Br into liquid solutions, capsules, and chewable tablet forms.

In powder or capsule form, Br should be stored at room temperature. Once formulated into a liquid solution, it should be kept refrigerated and discarded after 6 months.

Phenobarbital
Specimen Requirement     Serum (0.25 ml)
Turnaround Time     Daily (Mon.–Sat.)

Bromide
Specimen Requirement     Serum (0.25 ml)
Turnaround Time     Daily (Mon.–Sat.)

Please call laboratory for current test codes and pricing.
*Do not use serum separator gels tubes for measuring these drug levels.

References: Boothe, Vet Clin N Am 28(2): 411-448, 1998; Trepanier, Proc 17th ACVIM, 1999, pp 268-269; Ducoté, Compendium, July 1999, pp 638-639.