hey,
I am on Lithium, Topamax, and Lamictal(along with 2 other psych meds)

. I do see where you are at, but I don't quite know where you are with the weight issue. I am looking at d/c my Lithium because of weight gain(with pdoc's permission , of course). The Lamictal in combination with Topamax and one of my antipsychotics has really "leveled" my moods/paranoia/overall agitation, and kept my weight down. The doc says d/c Lithium would help with my weight loss.(I had gained a mountain of weight from Zyprexa). I don't think Topamax has been approved for treatment of BP, but it is a mystery to me why it works-I had some short term memory probs with it, but it might not affect you the same way it did for me.