<unk>  is an analgesic opioid that is FDA approved for the treatment of mild to moderate pain. There is a Black Box Warning for this drug as shown here.  Common adverse reactions include constipation, nausea, vomiting, dizziness, lightheadedness, sedation, somnolence, and dyspnea.
Codeine
Morphine 
Nalorphine
Normorphine
Meperidine 
Dihydrocodeine
Morpholine
Tipepidine