Some common side effects of this drug include: Headache, Nausea, Nosebleed, Stomach upset Keep in mind that your doctor has prescribed you this medication because its benefits to you are greater than the risk of side effects. Many people who use this medication do not have serious side effects. However, if you undergo any serious side effects as mentioned below then notify your doctor immediately. Unusual pain or swelling or discomfort, Unusual bruising, Prolonged bleeding from cuts or gums, Persistent or frequent nosebleeds, Unusually heavy or prolonged menstrual flow, Bloody or black stools, Bloody urine, Vomit that is bloody or looks like coffee grounds, Severe headache, Dizziness or fainting, Shortness of breath, Chest pain, Difficulty swallowing Prasugrel can cause blood disorder which is very rare but serious so if you develop any symptoms of this blood disorder, get immediate medical help. Vision changes, Slurred speech, Confusion, Dark urine, Unusual weakness or tiredness, Unexplained fever.