<unk>  is an opioid analgesic that is FDA approved for the treatment of management of moderate to moderately severe chronic pain in adults who require around-the-clock treatment of their pain for an extended period of time.   Common adverse reactions include seizure risk, suicide risk, serotonin syndrome, anaphylactoid and allergic reactions, respiratory depression, withdrawal symptoms.
Tramadol
Tapentadol
Hydrocodone
Etodolac
Oxycodone
Acetylmethadol
Morphine 
Nefazodone