Lady gets potassium bromide along with phenobarbital. She gets a pretty high dose of each because she gets cluster seizures. She weighed 7.2 last week at the vets. She gets 280 mg KBr before bed.
Since Oscar just started taking it, they will monitor his levels with bloodwork to make sure the dose is right.
Have you seen this website? It's been my "bible" for dealing with Lady's epilepsy for the last nine years:
Canine epilepsy and diseases that cause seizures in dogs