Norbinaltorphimine (nor-BNI or nBNI) is an opioid antagonist used in scientific research.

It is a highly selective inverse agonist for the κ-opioid receptor.

[1][2] In animals, nor-BNI blocks the effects of κ-opioids[3][4] with a slow onset and an exceptionally long duration of action (up to several months).

[5][6] It produces antidepressant-like[7] and anxiolytic-like effects in animal models.

[8] In the United States, the DEA considers nor-BNI a Schedule II substance as a derivative of noroxymorphone.