Medical management of recurrent seizures in dogs and cats

Disposition and clinical use of bromide in cats

OBJECTIVE

To establish a dosing regimen for potassium bromide and evaluate use of bromide to treat spontaneous seizures in cats.

DESIGN

Prospective and retrospective studies.

ANIMALS

7 healthy adult male cats and records of 17 cats with seizures.

PROCEDURE

Seven healthy cats were administered potassium bromide (15 mg/kg [6.8 mg/lb], p.o., q 12 h) until steady-state concentrations were reached. Serum samples for pharmacokinetic analysis were obtained weekly until bromide concentrations were not detectable. Clinical data were obtained from records of 17 treated cats.

RESULTS

In the prospective study, maximum serum bromide concentration was 1.1 +/- 0.2 mg/mL at 8 weeks. Mean disappearance half-life was 1.6 +/- 0.2 weeks. Steady state was achieved at a mean of 5.3 +/-1.1 weeks. No adverse effects were detected and bromide was well tolerated. In the retrospective study, administration of bromide (n = 4) or bromide and phenobarbital (3) was associated with eradication of seizures in 7 of 15 cats (serum bromide concentration range, 1.0 to 1.6 mg/mL); however, bromide administration was associated with adverse effects in 8 of 16 cats. Coughing developed in 6 of these cats, leading to euthanasia in 1 cat and discontinuation of bromide administration in 2 cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Therapeutic concentrations of bromide are attained within 2 weeks in cats that receive 30 mg/kg/d (13.6 mg/lb/d) orally. Although somewhat effective in seizure control, the incidence of adverse effects may not warrant routine use of bromide for control of seizures in cats.

Pharmacokinetic properties of bromide in dogs after the intravenous and oral administration of single doses

Bromide (20 mg kg-1) was administered intravenously and orally to normal beagle dogs. The mean (SD) apparent elimination half life (t1/2 beta) after oral administration (46 +/- 9 days) was not significantly different from the mean t1/2 beta after intravenous administration (37 +/- 10 days). The mean total body clearance was 9.0 +/- 3.9 ml day-1 kg-1 and the mean apparent volume of distribution was 0.45 +/- 0.07 litre kg-1. The mean area under the serum concentration time curve (AUC) was significantly smaller after oral administration than after intravenous administration, and from a comparison of the two values the oral bioavailability of bromide was estimated to be 46 per cent. Assuming this degree of bioavailability, the daily dose of bromide necessary to maintain serum bromide concentrations within the therapeutic range of 1000 to 2000 mg litre-1 recommended for epileptic dogs was estimated to be approximately 21 mg kg-1. The intravenous loading dose of sodium bromide necessary to reach minimal therapeutic serum bromide concentrations was predicted to be 570 +/- 90 mg kg-1.