I've been wondering the same exact thing, but have gotten nowhere. I looked online all it said is that things that cause drowsiness could be dangerous because the Topamax would intensify that. I'm on it too. I'm on 75 mg's a night. It's hard to tell what's causing what because I have a bad cold right now and am taking something for that. It may be ill-advised but noone is telling me anything and I have to do something. But I am very drowsy a lot. Often confused and forgetful...heh moreso than usual. It takes me longer to type things out and spell things. I'm more dizzy than I was before. (I had dizziness before. The neurologist claims it's part of the migrain) and best of all...I still have my migraines. It's been 3 nights at 75 mg's (built up from 25 mg's). So...I guess we'll see.