What a weird coincidence that I JUST switch from Lexapro to Wellbutrin XL about a month ago. Yes you do have to ween yourself off Lexapro first. For the first week of weening off Lexapro, you cut the Lexapro in half and take that, and then take one Wellbutrin Xl at 150 milligrams.Continue that for the whole week. The next week, you cut the Lexapro into 4ths and take one of those everyday, and the 150 of Wellbutrin XL. After that, you stop the Lexapro all together and start taking a higher dose of Wellburtin. I got bumped up to 300 mg, but it may be different for you.The highest the Wellbutrin goes is to 450 mg. The first month you take Wellburtin XL, you are going to notice side effects. For me, it was dizziness and feeling sick, especially after eating. I am glad I stuck with it though, because this medicine is really working for me! It is also helping me with the weight I gained while on Lexapro. I've already lost 19 pounds
Hope this helps!