Buprenorphine is an opioid, narcotic analgesic, but it has one unique property. Unlike morphine, fentanyl, hydrocodone, etc. that are potent opioid receptor agonists, buprenorphine is a mixed agonist/antagonist, which makes it ideal for recovering opioid abusers participating in rehab - it is combined with naloxone (an opioid antagonist) in a drug commonly known as SUBOXONE for that purpose. It's much more safer in overdose.

There are some indications that buprenorphine has some downfalls because of its mixed action, as some patients do report the same symptoms you reported. If the steroid injection fails to do the trick, I'd consider traditional narcotics like hydrocodone or fentanyl patches (DURAGESIC).