Reliever and fever reducer. The numbers 5-325 mg refer to the dosage of each ingredient in one tablet. The 5 represents 5 mg of hydrocodone, and the 325 represents 325 mg of acetaminophen. It is important to note that Norco is a controlled substance and can be habit-forming, so it should only be used under the guidance of a healthcare professional. Side effects and precautions should also be discussed with a healthcare provider.