Fioricet is a prescription medication primarily used to treat tension headaches. It is a combination drug that contains three active ingredients: Acetaminophen (also known as paracetamol): a pain reliever and fever reducer. Butalbital: a barbiturate that helps to relax muscle contractions in the head and neck. Caffeine: a stimulant that can enhance the effects of acetaminophen and help to constrict blood vessels, which may alleviate headache symptoms.