THERAPEUTIC SERUM DRUG CONCENTRATIONS IN EPILEPTIC DOGS TREATED WITH POTASSIUM-BROMIDE ALONE OR IN COMBINATION WITH OTHER ANTICONVULSANTS -122 CASES (1992-1996)

Objective-To determine therapeutic serum drug concentrations in epilep tic dogs treated with potassium bromide. Design-Retrospective study. A nimals-122 dogs with major motor epilepsy. Procedure-Medical histories were collected for epileptic dogs treated with potassium bromide with or without phenobarbital sodium or primidone, from which serum was su bmitted for bromide analysis from May 1992 to May 1996 to the Therapeu tic Drug Monitoring Program at Cornell University's College of Veterin ary Medicine. A therapeutic response (improved seizure control) was de fined as a greater than or equal to 50% reduction in seizure frequency following initiation of bromide treatment. Serum bromide and phenobar bital concentrations and therapeutic outcome were determined for all d ogs. Results-72% of epileptic dogs had a greater than or equal to 50% reduction in seizure frequency following initiation of treatment with potassium bromide. Discontinuation of barbiturate treatment was possib le in 19% of those dogs originally treated with phenobarbital or primi done. Of those dogs continued on bromide and phenobarbital, 450/0 main tained seizure control with serum phenobarbital concentrations < 20 mu g/ml. Significantly higher serum bromide concentrations were required when dogs were initially or eventually treated with bromide alone (me an bromide concentration, 1,906 mu g/ml) compared with dogs treated wi th potassium bromide along with a barbiturate (mean bromide concentrat ion, 1,621 mu g/ml). Clinical Implications-When dogs are treated with bromide and phenobarbital, a reasonable therapeutic range for serum br omide concentrations is 810 to 2,400 mu g/ml, and for bromide treatmen t alone, the range is 880 to 3,000 mu g/ml. When phenobarbital is used in combination with bromide, a reasonable therapeutic range for serum phenobarbital concentrations is 9 to 36 mu g/ml, although in some dog s treated with bromide, phenobarbital can eventually be discontinued.