can harm your liver, but only in
overdose quantities. The narcotics in the pain meds, like
hydrocodone, codeine, and others are usually not harmful to the liver. The thing the docs worry about is the potential for abuse and/or addiction. The abuse could easily lead to the overdose (on the acetaminophen) which is very dangerous, as Hector points out.
I asked my new doc for some Lortab, which I have found very helpful for the aches of TX along with increased frequency of migraine headaches.