Naltrexone, an opioid antagonist derived from the analgesic oxymorphone, was synthesized as EN-1639A by Blumberg and colleagues in 1967. Four years later, in 1971, naltrexone was selected for high-priority development as a treatment for opioid addiction by the Special Action Office for Drug Abuse Prevention, an office created by President Nixon and put under the leadership of Dr Jerome Jaffe.