Hi, thanks for asking in Health care magic. PRN is a latin word meaning as and when needed . Hydrocodone is an opioid analgesic (pain killer of high intensity) and is given for severe pain. Hydrocodone is capable of causing addiction and dependence if given regularly but not otherwise. Since it was indicated only as PRN your mother s nurse would have given her the medication only when she needed it and so it would not produced any dependence for your mother. Tylenolol is Acetaminophen/Paracetamol and is available as over the counter drug. It is a mild analgesic compared to Hydrocodone. The mere fact that your mother s Dr has changed the prescription to Acetaminophen indicates that she is not dependent or addicted to Hydrocodone. Withdrawal symptoms of Hydrocodone is severe and the drug should not be stopped suddenly in people who are dependent on it. But in your mother s case since she was not dependent on the drug, no ethical issue arises. You can give Tylenol if she has pain and you don t need to wait for her nurse. I hope this is useful to you.