Side effects that may occur while taking Requip XL include: Constipation, Dizziness, Drowsiness, Fatigue, Headache, Increased sweating, Diarrhea, Dry mouth, Sweating, Lightheadedness, Loss of appetite, Nausea, Anxiety, Insomnia, Sore throat or flu-like symptoms, Stomach pain or upset, Tiredness, Vomiting, Weakness If the side effects persist or worsen, contact your doctor immediately. In case of any allergic reactions such as hives, difficulty breathing, swelling of your face, lips, tongue, or throat, you need to get immediate medical help. In case of any serious side effects, seek immediate medical help. Severe side effects include: Feeling like you might pass out, Fever, Stiff muscles, Confusion, Sweating, Fast or irregular heartbeats, Hallucinations, Fall asleep during a daily activity, Fainting, Tremors, Tight feeling in your chest, Trouble breathing