Fentanyl, primarily used as an anesthetic over the last half century, has become the new covert drug, and some drug users are paying with their lives. Over 300 people have died since 2008 from Fentanyl, which can be passed off wrongly as heroin. The drug causes the chest muscles to freeze (which is why it's an anesthetic in normal circumstances), and is "30 to 40 times more powerful that heroin." Police forces need to crack down and find out how drug chefs are finding the supplies.
Image Source: By BQT QT (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons