Fentanyl Surpasses Heroin As Drug Most Often Involved In Deadly Overdoses Fentanyl Surpasses Heroin As Drug Most Often Involved In Deadly Overdoses When fentanyl, a synthetic opioid 50 to 100 times more powerful than morphine, infiltrated the drug supply in the U.S. it had an immediate, dramatic effect on the overdose rate. Read this story This email was sent by: NPR,1111 N. Capitol St. NE Washington, DC, 20002, United States. This message was sent to .