Imepitoin has recently been approved in Europe for the management of dogs with idiopathic
epilepsy. Currently, there is no evidence-based information available on the efficacy of
antiepileptic drugs used as additions to the therapeutic regimen in dogs with idiopathic
epilepsy that are not well controlled with
imepitoin. The goal of this study was to evaluate the efficacy of
phenobarbital or
potassium bromide (
KBr) as add-on
antiepileptic drugs for controlling dogs refractory to a maximum dose of
imepitoin (30 mg/kg twice daily). The study was performed as a prospective, randomised, controlled clinical trial. The efficacy of
phenobarbital and
KBr was evaluated by comparing monthly seizure frequency (MSF), monthly seizure day frequency (MSDF), the presence of cluster
seizures during a retrospective 2-month period with a prospective follow-up of 6 months, and the overall responder rate. Twenty-seven dogs were included in the study, 14 dogs in the
phenobarbital group and 13 dogs in the
KBr group. Both median MSF and MSDF decreased in the
phenobarbital group (both P = 0.001) and in the
KBr group (P = 0.004 and P = 0.003, respectively). Overall, the number of dogs with cluster
seizures decreased (P = 0.0005). The responder rate was 79% vs. 69% in the
phenobarbital and
KBr groups, respectively. We conclude that
phenobarbital or
KBr add-on treatment decreases median MSF and MSDF in epileptic dogs refractory to a maximum dose of
imepitoin. Combination
therapy was generally well tolerated and resulted in an improvement in seizure management in the majority of the dogs.