Fentanyl is all the things that people said it was on this thread (pain killer, used as patch etc.) but its primary role in life is as a synthetic narcotic used in anethesia. Certain forms of anesthesia require high does narcotics which typically get combined with other pharmacology to concoct an anesthetic "cocktail". Fentanyl was a "designer" narcotic built to meet this specific need. It is something like 5x (or 10x I forget which) more potent than morphine and presumably also more potent than heroin. Sounds like people that got hold of some of this drug are now sleeping "The Big Sleep". Guess there's yet another reason not to be an iv drug abuser.
Fentanyl is a synthetic narcotic that is very potent ( dose is measured in micrograms where morthine is in milligrams), and also very short acting. this makes it a GREAT drug to use for anesthesia or painful procedures. You can give the patient a reversal agent like Narcan and be sure the narcan will last longer then the fentanyl making it safer to use.
There's also sufentanil which is 100 times as potent as fentanyl.....
drug users have been known to go after USED patches, patches that have been removed after the three day period.....talk about desparate...