"Fentanyl was detected in 56.3% of 5,152 opioid overdose deaths in the 10 states during July–December 2016 (Figure). Among these 2,903 fentanyl-positive deaths, fentanyl was determined to be a cause of death by the medical examiner or coroner in nearly all (97.1%) of the deaths.
"Fentanyl is a synthetic opioid analgesic acting predominately at the μ-opiate receptor. It has historically been used as a pain reliever and an anaesthetic in both human and veterinary medicine and in terms of analgesic activity it is at least 80 times more potent than morphine. Fentanyl was first synthesized by Paul Janssen in 1960 and marketed as a medicinal product for treating pain. Subsequently, many fentanyl analogues were developed including sufentanil, alfentanil, remifentanil, and carfentanil.