(like heroin metabolized into morphine) Buprenorphine itself is a partial agonist at the mu opiate receptor, and
a full agonist at the delta and
competitve antagonist at the kappa receptor. Buprenorhpine's metabolizes into norbuprenorphine, which is a full opiate agonist at the mu, delta. noci, and partial agonist at the kappa. So basically they are computing at all your opioid receptors, except the mu.