Fentanyl is a synthetic opioid that is about 100 times more potent than morphine. The powerful painkiller has been linked to an increase in fatal overdose deaths across the United States, and authorities suspect dealers are using it because it’s cheap to produce and more profitable than heroin.Read more: The ultra-potent synthetic heroin that’s sweeping the U.S.Watch: A DEA chemist explains why powerful synthetic heroin is killing so many people.