In general, Wellbutrin takes about 4 weeks to start working. Side effects of Wellbutrin
SR include agitation, constipation
, dizziness, dry mouth, insomnia, nausea, rash, sweating, and/or weight loss. Side effects of Wellbutrin XL may include abdominal pain, agitation, anxiety, constipation, diarrhea, dizziness, dry mouth, heart palpitations, increased urination, insomnia, muscle soreness, nausea, rash, ringing in the ears, sore throat, and/or sweating.