Norco (hydrocodone/acetaminophen) and Tylenol (acetaminophen) should not be taken together.
Norco is a combination of two products, hydrocodone (which is known as an opioid and is similar to morphine and codeine), and acetaminophen.
Tylenol is an analgesic that contains the active ingredient acetaminophen, the same ingredient that is contained in Norco. Taking both Norco and Tylenol together will result in a duplication of therapy and possibily over dosing on acetaminophen.
Taking too much acetaminophen can cause severe liver problems. In fact, hydrocodone combination products such as Norco used to contain much higher levels of acetaminophen, up to 650 mg. In 2011, the FDA limited the amount of acetaminophen that could be contained in opioid containing products to 325 mg to avoid the risk of liver injury.
If you need to take another analgesic in between doses or as an add on to Norco, you may take ibuprofen (Advil, Motrin) as there is no interaction between it and Norco.