Serious side effects of this drug include fast heartbeat, slow heart rate (< 60 beats per minute), shortness of breath, swelling, pounding heartbeat, confusion, fever, pale skin, decreased urinary output, hallucinations, rapid weight gain, and inability to urinate. Other side effects include dizziness, dry eyes, dry mouth, nausea, headache, vomiting, mild skin rash, nighttime urination, decreased libido, muscle pain, and joint pain.