I've taken 75 mg of Wellbutrin for 4 weeks. I didn't notice any difference. Doc increased my dose to 150mg xl. I've been on this for almost 4 weeks also. So that's 8 weeks altogether. I'm guessing it will work within the next two week. I would like to hear from others who are on 150mg xl Wellbutrin also and their expire nice with it. Thanks:)