Side effects that may occur while taking this medication include: Involuntary movements, Dizziness, Drowsiness, Loss of appetite, Worsened RLS symptoms early in the morning, Sweating, Diarrhea, Excessive tiredness, Anxiety, Headache, Upset stomach, Heartburn, Mild nausea, Vomiting, Constipation, Frequent urination, Insomnia, Dry mouth, Decreased sexual ability. In case of the following serious side effects, seek immediate medical help. Feeling like you might pass out, Fever, Stiff muscles, Confusion, Sweating, Irregular heartbeats, Hallucinations, Tremors or tight feeling in your chest, Trouble breathing