The reason Demerol is dangerous is because of the toxic metabolite called normeperidine. This is why you can't safely take anymore then 400mg's in a day max and you can't take it at high doses for longer then 3 days as normeperidine has a much longer half life then meperidine and it accumulates over time. So unlike oxycodone, morphine, hydromorphone, fentanyl and every other typical opiate/opioid it is actually toxic and narcan doesn't help the toxic effects caused by normeperidine such as hallucinations, seizures, cardiotoxicity and a few other things i am probably forgetting. It's not the opioid effects that makes Demerol dangerous it's the atypical toxic effects special to Demerol. It has anti-cholinergic effects as well this is why Demerol tends to make people alot more spaced out then say morphine
I know people who still get it prescribed here where i live but it's even becoming rare here where as 10 years ago it was still a first line opioid in treating any type of moderate to moderately severe pain. It's absolutely useless for chronic pain since you can't take it everyday, has very short acting analgesic effects and it's not a very strong opioid anyway so that's another reason it's fallen out of favor. It is still used alot in ER settings for certain types of pain such as migraines and such since for some odd reason Demerol seems to work well for migraine pain. The only advantages it has over other opioids is that it causes less respiratory depression then say morphine, hardly causes any histamine release and causes very little constipation.