Ibogaine and related compounds bind to various opioid receptors, with ibogaine showing affinity for kappa-opiate receptors (Ki = 2.08 µM), while harmaline and harmine do not bind to opiate receptors. All tested drugs also affect sodium channels at micromolar concentrations, but neither ibogaine nor harmaline interacts with GABA receptors. The kappa-opioid activity may explain ibogaine's proposed anti-addictive effects, while sodium channel effects could account for the tremor-inducing properties of ibogaine and harmaline.
Noribogaine, a suspected metabolite of ibogaine, binds more strongly than ibogaine to all three types of opioid receptors. Ibogaine had highest affinity for kappa receptors, less for mu, and no measurable affinity for delta receptors. Noribogaine showed higher affinity for kappa, mu, and delta receptors, suggesting it is active in the body and may contribute to ibogaine's effects.