I never drank much alcohol anyway, the occasional g and t, glass of champagne, or Pimms, but as the Topiramate made any fizzy drink taste absolutely disgusting (including fizzy water) I couldn't drink anything with a fizz. Also couldn't drink, juices, tea, coffee or milk. My only beverage was tap water for over a year!
Like Jasper, in addition to the usual migraine disconnect, my brain stopped computing. I couldn't remember names, place faces, find words: to the extent that normal conversations became really laboured and difficult. Cocktail parties, or instances where I'd meet new people were a nightmare because I could see the confusion on their faces. I couldn't find my words (hah, not a problem I struggle with usually!) to enable me to maintain a normal conversation. Someone actually asked a friend if I'd had a stroke!
The list of side effects were endless for me and at the end really quite frightening however, at my final hospital appointment when I really was very poorly, I met a woman who had been taking it for years. She'd had six difficult weeks at the beginning and then all calmed and it reduced her chronic migraine from a 9 to a 2, which she felt she could live with. 
Just to repeat, we are all very different and will react to meds in our own unique ways! Ask your family to be aware of your mental state and to advise you if things start to change. I had never had any mental health problems, never even mood changes with PMT, in fact despite the fact that I am hugely sensitive to hormone change it has never affected me mentally. However, at nine months on this med my moods became dark and I became angry. I'm a tough old bird anyway, but nobody would have dared to ‘mess' with me then!