Norbuprenorphine-3-glucuronide
Norbuprenorphine-3-glucuronide (N3G) is a major active metabolite of the opioid modulator buprenorphine.[1] It has affinity for the κ-opioid receptor (Ki = 300 nM) and the nociceptin receptor (Ki = 18 μM), but not for the μ- or δ-opioid receptors.[1] Whether N3G acts as an agonist or antagonist of each of the former two respective sites has yet to be determined.[2] In animals, N3G has been found to produce sedation, decreased locomotion, and a small amount of antinociception, properties which are consistent with the effects of κ-opioid receptor agonists.[1] In addition, N3G has been found to reduce tidal volume but not respiratory rate.[1] Unlike norbuprenorphine, but similarly to buprenorphine and buprenorphine-3-glucuronide, N3G is not a substrate for P-glycoprotein.[2] However, due to its highly hydrophilic nature, N3G nonetheless passes the blood-brain-barrier in only very small amounts.[2] See alsoReferences
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