<unk> (injection) is an opioid analgesic that is FDA approved for the treatment of pain. There is a Black Box Warning for this drug as shown here.  Common adverse reactions include lightheadedness, dizziness, sedation, nausea, vomiting, sweating, flushing, dysphoria, euphoria, dry mouth, and pruritus.
Hydromorphone 
Oxymorphone 
Morphine 
Nalorphine
Normorphine
Ropivacaine
Butorphanol 
Meperidine 