I'm on Lamotrigine and overall have found it really good. A bit bumpy in the ramp up but overall very good. I know I was anxious as I increased my dosage, which made me kind of more alert to the way I was feeling, as I was looking for side effects. From what I have been told by my Pdoc, Lamotrigine usually works pretty fast, so a dosage change is going to affect you fast as it doesn't need to build up in your system like other mood stabilizers. Stick with it, but keep notes so you can tell you Pdoc what is going on. If the symptoms get too bad get on the phone to him and get some advice, or alternately if you don't think you can keep taking the 300 or feel in danger, you have the option of going back to your 200mg and waiting till you see him next.