one being tolerance, where any pain medication will slowly lose
effectiveness, and the other being the anatomical source of the pain. Any relief from a narcotic (oxycodone, hydrocodone, demerol etc) will, be shot-lived; The receptors for pain medication in your brain simply adjust to whatever you are taking, and the dose must be increased to relieve the pain again. At some point you will run out of room to keep going up on the dose.