It may be a toothache. Or, if it seems to be more a behavior thing, give her some benadryl.
One of our dogs has spells where he would go manic, trying to eat all the grass he could find and oblivious to everything around him. He would also be gulping, like he was trying to swallow, not unlike hiccups. It seems to be some sort of seizure. The best treatment seems to be benadryl.
But yeah, it could also be that the poor dog has had enough and is desperately seeking mescaline.