Fentanyl, which looks like heroin, is a powerful synthetic painkiller that has been laced into heroin but is increasingly being sold by itself — often without the user’s knowledge. It is up to 50 times more powerful than heroin and up to 100 times more potent than morphine. A tiny bit can be fatal.
http://www.nytimes.com/2016/03/26/us/heroin-fentanyl.html?partner=rss&emc=rss&_r=1
