Impact of CYP2D6 Polymorphisms on the Pharmacokinetics of N,N-Dimethyltryptamine and Harmine via PBPK Modeling and Simulation

Background/Objectives: In this study, we present an analysis of ayahuasca, a psychedelic preparation containing N,N-dimethyltryptamine (DMT) and β-carbolines, such as harmine (HRM), a reversible monoamine oxidase A (MAO-A) inhibitor that enables the oral bioavailability of DMT. CYP2D6 is a highly polymorphic enzyme associated with interindividual variability in drug exposure, but its influence on the pharmacokinetics of ayahuasca alkaloids remains poorly understood. Methods: Using physiologically based pharmacokinetic (PBPK) modeling, we simulated scenarios for poor (PM), normal (NM), and ultra-rapid (UM) metabolizers by adjusting CYP2D6 enzyme expression for each phenotype. Results: PMs showed increased systemic exposure to DMT (AUC +53.3%; Cmax +40.5%) and HRM (AUC +30.6%; Cmax +22.8%), while UMs exhibited reduced exposure to both compounds. Conclusions: These findings highlight the significant impact of CYP2D6 polymorphisms on the pharmacokinetics of DMT and HRM, reinforcing the value of PBPK modeling for predicting interindividual variability and potential clinical risks.