Potassium Bromide is a mild sedative. It was discontinued in humans in the early 1900s when better drugs, such as phenobarbitone were discovered.
Potassium bromide is another drug they give to control seizures, but I can't tell you anything about it. I believe it is a 2nd line drug that they use only if pheno doesn't help. But you won't know if pheno is helping or not unless he takes it regularly so that his level reaches therapeutic range, which will take a few weeks.
With regards,
Geoffrey