18-Methoxycoronaridine (18-MC) and ibogaine: comparison of antiaddictive efficacy, toxicity, and mechanisms of action.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and in vitro mechanistic evaluation
PubMed 11085336 · doi:10.1111/j.1749-6632.2000.tb05211.x
What was done
The authors compared the synthetic congener 18-methoxycoronaridine (18-MC) with ibogaine across several rodent models of addiction and in vitro assays. They evaluated 40 mg/kg doses on intravenous self-administration of morphine and cocaine, oral self-administration of ethanol and nicotine, and responding for water. They also assessed opioid withdrawal signs, extracellular dopamine and serotonin levels in the nucleus accumbens, drug-induced dopamine release, locomotor effects, toxicity (tremors, cerebellar histology at doses up to ≥ 100 mg/kg, and heart rate), receptor binding affinities, and pharmacokinetics.
What was found
Both 18-MC and ibogaine (40 mg/kg) decreased self-administration of morphine, cocaine, ethanol, and nicotine in rats and ameliorated opioid withdrawal signs. Unlike ibogaine, 18-MC did not alter responding for water. Both decreased basal accumbens dopamine and blocked morphine- and nicotine-induced dopamine release, but only ibogaine increased accumbens serotonin and enhanced cocaine-induced dopamine elevations. Ibogaine produced whole-body tremors, cerebellar damage at doses ≥ 100 mg/kg, and bradycardia at high doses; 18-MC produced none of these toxicities. In binding assays, 18-MC matched ibogaine's affinity for kappa opioid and nicotinic receptors but had much lower affinity for NMDA and sigma-2 receptors, sodium channels, and the serotonin transporter.
Why it matters
18-MC retains the broad anti-addictive properties of ibogaine in animal models while eliminating key neurotoxic and cardiovascular liabilities, indicating a substantially higher therapeutic index.
Limits
The findings are derived entirely from rat models and in vitro receptor assays, precluding direct conclusions about human safety or efficacy. The abstract reports no sample sizes, variance measures, or quantitative effect sizes for the behavioral and physiological outcomes.
Cited by
- supports Administering ibogaine to rodents trained to self-administer alcohol causes them to stop self-administering alcohol.