Ibogaine Pharmacology

The pharmacology of ibogaine is quite complex, affecting many different neurotransmitter systems simultaneously.Because of its fairly low potency at any of its target sites, ibogaine is used in doses anywhere from 5 mg/kg of body weight for a minor effect to 30 mg/kg in the cases of strong polysubstance addiction. It is unknown whether doses greater than 30 mg/kg in humans produce effects that are therapeutically beneficial, medically risky, or simply prolonged in duration. In animal neurotoxicity studies, there was no observable neurotoxicity of ibogaine at 25 mg/kg, but at 50 mg/kg, one-third of the rats had developed patches of neurodegeneration, and at doses of 75 mg/kg or above, all rats showed a characteristic pattern of degeneration of Purkinje neurons, mainly in the cerebellum. While caution should be exercised when extrapolating animal studies to humans, these results suggest that neurotoxicity of ibogaine is likely to be minimal when ibogaine is used in the 10–20 mg/kg range typical of drug addiction interruption treatment regimes, and indeed death from the other pharmacological actions of the alkaloids is likely to occur by the time the dose is high enough to produce consistent neurotoxic changes.

Pharmacodynamics

Ibogaine affects many different neurotransmitter systems simultaneously.

Noribogaine is most potent as a serotonin reuptake inhibitor. It acts as a moderate κ-opioid receptor agonist and weak µ-opioid receptor agonist or weak partial agonist. It is possible that the action of ibogaine at the kappa opioid receptor may indeed contribute significantly to the psychoactive effects attributed to ibogaine ingestion; Salvia divinorum, another plant recognized for its strong hallucinogenic properties, contains the chemical salvinorin A, which is a highly selective kappa opioid agonist. Noribogaine is more potent than ibogaine in rat drug discrimination assays when tested for the subjective effects of ibogaine.

Pharmacokinetics

Ibogaine is metabolized in the human body by cytochrome P450 2D6 into noribogaine (more correctly, O-desmethylibogaine or 12-hydroxyibogamine). Both ibogaine and noribogaine have a plasma half-life of around two hours in the rat, although the half-life of noribogaine is slightly longer than that of the parent compound. It is proposed that ibogaine is deposited in fat and metabolized into noribogaine as it is released. After ibogaine ingestion in humans, noribogaine shows higher plasma levels than ibogaine and is detected for a longer period of time than ibogaine