Norbuprenorphine

Norbuprenorphine is the primary active metabolite of buprenorphine. Norbuprenorphine acts as a μ-opioid, δ-opioid, and nociceptin receptor full agonist, as well as a κ-opioid receptor partial agonist. Norbuprenorphine crosses the blood-brain-barrier similarly to buprenorphine and likely contributes to its effects.