Noribogaine is the principal psychoactive metabolite of the hallucinogenic drug ibogaine. It is thought to be involved in the antiaddictive effects of ibogaine-containing plant extracts, such as Tabernanthe iboga. A recent study evaluated its effects on healthy volunteers at doses of 3–60 mg, finding no tolerability issues. A slow half-life of 28–49 hours was seen with large volume of distribution. Noribogaine is a potent serotonin reuptake inhibitor, but does not affect the reuptake of dopamine. Unlike ibogaine, noribogaine does not bind to the sigma-2 receptor. Similarly to ibogaine, noribogaine acts as a weak NMDA receptor antagonist and binds to opioid receptors. It has greater affinity for each of the opioid receptors than does ibogaine. Recently, noribogaine has been determined to act as a biased agonist of the κ-opioid receptor (KOR).
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