Ibogaine is a psychoactive alkaloid that possesses potential as an agent to treat opiate and cocaine addiction. The primary metabolite arises via O- demethylation at the 12-position to yield 12-hydroxyibogamine. In this report, evidence is presented that the O-demethylation of ibogaine observed in human hepatic microsomes is catalyzed primarily by the polymorphically expressed cytochrome P-4502D6 (CYP2D6). An enzyme kinetic examination of ibogaine O-demethylase activity in pooled human liver microsomes suggested that two (or more) enzymes are involved in this reaction: one with a low K(Mapp) (1.1 μM) and the other with a high K(Mapp) (>200 μM). The low K(Mapp) activity comprised >95% of total intrinsic clearance. Human liver microsomes from three individual donors demonstrated similar enzyme kinetic parameters (mean K(Mapp) = 0.55 ± 0.09 μM and 310 ± 10 μM for low and high K(M) activities, respectively). However, a fourth human microsome sample that appeared to be a phenotypic CYP2D6 poor metabolizer possessed only the high K(Mapp) activity. In hepatic microsomes from a panel of human donors, the low K(Mapp) ibogaine O-demethylase activity correlated with CYP2D6- catalyzed bufuralol 1'-hydroxylase activity but not with other P450 isoform- specific activities. Quinidine, a CYP2D6-specific inhibitor, inhibited ibogaine O-demethylase (IC50 = 0.2 μM), whereas other P450 isoform- specific inhibitors did not inhibit this activity. Also, of a battery of recombinant heterologously expressed human P450 isoforms, only rCYP2D6 possessed significant ibogaine O-demethylase activity. Thus, it is concluded that ibogaine O-demethylase is catalyzed by CYP2D6 and that this isoform is the predominant enzyme of ibogaine O-demethylation in humans. The potential pharmacological implications of these findings are discussed.
|Original language||English (US)|
|Number of pages||5|
|Journal||Drug Metabolism and Disposition|
|State||Published - Aug 1 1998|
ASJC Scopus subject areas
- Pharmaceutical Science