Tapentadol is an opioid pain medication. An opioid is sometimes called a narcotic.Tapentadol is a prescription medicine that is used to treat moderate to severe pain. Tapentadol extended-release form (Nucynta ER) is for around-the-clock treatment of pain that is not controlled by other medicines. The extended-release form of tapentadol is not for use on an as-needed basis for pain.