
One of my boys suffered from high liver enzymes due to long term anti seizure medication following suspected mild brain damage. The best thing we ever did for him was to put him onto a raw diet. His enzymes were reduced by over a 3rd in 3 months (and falling), and he was so much better for it. It might not be something that you would consider but i would certainly recommend either raw or a natural diet. But with any diet change for a dog on medication please make sure you speak to the vet about it first.
Good Luck