Allosteric inhibition of AC could also explain why iboga alkaloids administered alone do not produce signs of opioid overdose, but potentiate the toxicity of opioids [30,36,73,90,91], and why iboga alkaloids diminish, rather than exacerbate withdrawal signs in opioid dependence [4-6,12-25] despite the present finding of an MOR antagonist action. This evidence concerns the gene OPRM1 and opiate dependence.