I agree with some of the posters that this is a provider problem. If the ED physician or NP or PA wasn't handing the narcs out so easily, there would be less of a problem. I know one local facility that became "known" as the place where you could get narcs for any complaint - it got to the point where the HCPs were being harrassed just trying to get to their cars! Ridiculous. Eventually, the provider who was writing for the narcs lost his license. People who use and abuse narcotics quickly find out what facilities hand out the narcs the easiest, and flock to them.
As a nurse, you have to be cautious here. You aren't the provider writing for the meds, and you don't want to put yourself in between the drug-seeking patient and the physician who diagnosed the pain and wrote the scripts. I agree with the poster who talked about narcotic contracts. That would be an idea you as the nurse could present, take charge of, and make a policy that the physicians would have to follow. Neatly circling around the MDs/etc, who would have to comply with policy.
If it gets really bad, to the point where it's dangerous for you to walk out -- there is always the DEA. I can think of a patient who was identified as a drug-seeker, the police were called, and they were arrested. Narcotic diversion is an arrestable offense in my state.