Cytochrome P4502D6 catalyzes the O-demethylation of the psychoactive alkaloid ibogaine to 12-hydroxyibogamine.
Level 5 - mechanism / opinion, no new human data
In vitro bench research using human liver microsomes and recombinant enzymes
What was done
The study investigated the enzymatic mechanism of ibogaine O-demethylation to 12-hydroxyibogamine in vitro. The authors evaluated enzyme kinetics in pooled human liver microsomes, microsomes from individual human donors (including three standard donors and one phenotypic CYP2D6 poor metabolizer), and a panel of recombinant heterologously expressed human P450 isoforms. They performed correlation analyses against isoform-specific activities (such as bufuralol 1'-hydroxylation for CYP2D6) and selective chemical inhibition experiments using the CYP2D6 inhibitor quinidine alongside other P450-specific inhibitors.
What was found
Pooled human liver microsomes exhibited biphasic kinetics involving a low apparent Km (KMapp = 1.1 µM), which accounted for >95% of total intrinsic clearance, and a high KMapp (>200 µM). Three individual donor microsome samples showed similar kinetics (mean KMapp = 0.55 ± 0.09 µM for low Km; 310 ± 10 µM for high Km), whereas a phenotypic CYP2D6 poor metabolizer sample exhibited only the high KMapp activity. Low KMapp ibogaine O-demethylase activity correlated specifically with CYP2D6 bufuralol 1'-hydroxylase activity across a donor panel. Quinidine inhibited the reaction with an IC50 of 0.2 µM, and among recombinant enzymes tested, only rCYP2D6 showed significant ibogaine O-demethylase activity.
Why it matters
This identifies CYP2D6 as the principal enzyme responsible for ibogaine O-demethylation in humans. Because CYP2D6 is highly polymorphic, individual differences in genotype or concurrent use of CYP2D6 inhibitors could lead to major variations in ibogaine metabolism, clearance, and toxicity.
Limits
The study relies strictly on in vitro human liver microsome and recombinant enzyme assays; it does not measure in vivo pharmacokinetics, clearance, or clinical effects in living human subjects. Detailed kinetic comparisons in individual donors were limited to only four human liver samples.
Cited by
- supports Noribogaine exhibits a cardiac risk profile similar to ibogaine, and ibogaine is metabolized into noribogaine via the CYP2D6 enzyme over roughly 8 to 12 hours.