The most common neurologic disorder in dogs is primary epilepsy. Up to 50% of dogs diagnosed with the disease eventually have inadequate seizure control on phenobarbital (PB) therapy. Other dogs on PB develop hepatotoxicity, forcing its discontinuation. Another antiepileptic therapy, potassium bromide (KBr), is used in combination with PB and in some patients can be effective alone. Serum levels of bromide in the 200- to 300-mg/dl range are necessary for seizure control in many patients, and in some cases therapeutic concentrations may approach the toxic range. The goal of this study was to establish a safe and effective protocol for chronic oral KBr therapy in dogs. Healthy beagles were given 30 mg/kg doses of KBr Q 12 H for 115 days. Bromide concentrations in the serum, urine, and cerebrospinal fluid were measured. The median elimination half-life was 15.2 days, and the steady-state serum concentration was 245 mg/dl.

The chloride content of a diet directly affects bromide pharmacokinetics. In this study, chloride intake was in the low to middle range when compared with other commercial and prescription diets. Restricting dietary chloride increases tubular reabsorption of bromide, and increasing chloride concentrations increases renal clearance, shortening the elimination half-life.

This protocol produced bromide concentrations needed for seizure control in epileptic dogs. More studies are needed to determine if there are breed differences in bromide kinetics and to evaluate administration with other antiepileptic drugs, such as PB.

Pharmacokinetics and toxicity of bromide following high-dose oral potassium bromide administration in healthy beagles. March PA, Podell M, Sams RA. J VET PHARMACOL THERAP 25:425-432, 2002.