<unk> (injection) is an analgesic that is FDA approved for the treatment of moderate to severe pain and opioid dependence in patients unable to take oral medication.   Common adverse reactions include pruritis, urticaria, abdominal pain, anorexia,constipation, dry mouth, glossitis, asthenia, edema and headache.
Methadone 
Levomethadone
Morphine 
Morpholine
Buprenorphine 
Codeine
Naltrexone 
Acetylmethadol