Sometimes it's a matter of your body adjusting to a new medication. I remember when I first started taking Tegretol (carbamazpine) that I had dizziness and even momentary blackouts, of sorts. As for the latter, I had a couple driving incidents where I went through stop signs, a couple traffic lights, and down one-way streets/lanes in my own town, where I knew all of the streets. Hopefully fainting won't happen to you again. That certainly is concerning. Maybe your low blood pressure caused your fainting?

I had polyuria/polydipsia (sp?) while on Lithium, but not valproic acid. Who knows how things work. In any case, I hope your body will soon adjust to the new medication. Please do be patient, if your psychiatrist suggests it. I was grateful that I was patient through some of my initial Tegretol side effects. They went away in a matter of weeks.