Antonina~no I don't notice a brain fog. It does make me sleepy. It does come in 15mgs and I've been on it for a while, so they upped it cause I was having to take to many of the 15s. When I first started several years ago, I would take 1/2 of the 15 and it would knock the pain out or at least make it annoying and bearable. It never goes away. I haven't found that miracle pain pill yet...but I'm hoping.