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Numerical Analysis of Time-Dependent Inhibition by MDMA.

John T Rodgers¹, Jeffrey P Jones²

¹Department of Chemistry, Washington State University, Pullman, Washington.

Drug Metabolism and Disposition: the Biological Fate of Chemicals

|October 24, 2019

Summary

Methylenedioxymethamphetamine (MDMA) is not an irreversible inhibitor of CYP2D6. Computational models show MDMA exhibits slowly reversible inhibition, challenging previous findings.

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Area of Science:

Pharmacology
Drug Metabolism
Computational Chemistry

Background:

Methylenedioxymethamphetamine (MDMA) is a controlled substance with prior studies suggesting irreversible CYP2D6 inhibition.
Classic pharmacokinetic analyses may not fully capture complex drug-enzyme interactions.

Purpose of the Study:

To re-evaluate the mechanism of MDMA inhibition on CYP2D6.
To differentiate between irreversible and reversible time-dependent inhibition kinetics.

Main Methods:

Progress curve experiments using human liver microsomes and CYP2D6 baculosomes.
Numerical modeling to fit percentage of remaining activity (PRA) data.
Assessment of quasi-irreversible (QI) and equilibrium (EM) kinetic models.

Main Results:

Residual metabolism of MDMA showed a terminal linear phase in both human liver microsomes and baculosomes.
Numerical modeling indicated that an irreversible inhibition pathway was not necessary for a good fit.
Both QI and EM models provided good fits to the PRA data, suggesting slowly reversible inhibition.

Conclusions:

MDMA is not an irreversible inactivator of CYP2D6.
MDMA exhibits slowly reversible inhibition kinetics.
Computational modeling is crucial for accurately characterizing time-dependent enzyme inhibition.