RADIOLIGAND-BINDING STUDY OF NORIBOGAINE, A LIKELY METABOLITE OF IBOGAINE

Radioligand-binding studies were performed to ascertain the actions of noribogaine, a suspected metabolite of ibogaine, on opioid receptors. Consistent with previous results, ibogaine showed highest affinity for kappa opioid receptors (K-i = 3.77 +/- 0.81 mu M), less affinity for mu receptors (K-i = 11.04 +/- 0.66 mu M) and no affinity for delta receptors (K-i > 100 mu M). Noribogaine showed a higher affinity than ibogaine for all of the opioid receptors: kappa K-i = 0.96 +/- 0.08 mu M, mu K-i- = 2.66 +/- 0.62 mu M and delta K-i = 24.72 +/- 2.26 mu M. These data suggest that noribogaine is active in vivo and that it may contribute to ibogaine's pharmacological effects.