Fioricet is a medicine that’s used to treat pain and reduce anxiety. The active ingredient in Fioricet is acetaminophen, which the FDA has approved for use in children as young as six months old and adults up to 64 years old. There are several types of medications that contain acetaminophen, but there are also over-the-counter options such as Motrin or Aleve. Acetaminophen works by decreasing inflammation in your body, which helps to lower your fever or relieve pain associated with arthritis or muscle aches from exercise or injury.