<unk> (rectal) is a analgesic opioid that is FDA approved for the treatment of the relief of severe chronic pain, and severe acute pain.   Common adverse reactions include lightheadedness, dizziness, sedation,somnolence, nausea, vomiting, constipation,  and sweating.
Morphine 
Codeine
Morpholine
Normorphine
Nalorphine
Methadone 
Meperidine 
Benzidine