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Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance01:23

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MDMA-induced CYP2D6 inhibition: concentration-dependent variability using dextromethorphan as a probe.

Faezeh Ahmadi1, Hoda Lavasani1, Mohammadhosein Keshvadi1

  • 1Biopharmaceutics and Pharmacokinetics Division, Pharmaceutics Department, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, The Islamic Republic of Iran.

Drug Metabolism and Personalized Therapy
|June 16, 2026
PubMed
Summary

MDMA (Ecstasy) inhibits CYP2D6 enzyme activity, but recovery time depends on dextromethorphan concentration. Therapeutic levels showed inhibition only at 1 hour, while saturated levels showed prolonged inhibition, highlighting metabolite-dependent enzyme behavior.

Keywords:
dextromethorphanecstasyisolated perfused rat livermetabolismmirtazapinetramadol

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Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications

Published on: January 27, 2014

Area of Science:

  • Pharmacology
  • Drug Metabolism
  • Toxicology

Background:

  • MDMA (Ecstasy) abuse is prevalent due to its entactogenic effects.
  • Previous studies indicated MDMA inhibits CYP2D6, but enzyme recovery varied with different substrates.
  • Dextromethorphan is a well-established probe for assessing CYP2D6 activity.

Purpose of the Study:

  • To investigate the inhibitory effects of MDMA on CYP2D6 using dextromethorphan as a probe.
  • To clarify observations regarding CYP2D6 enzyme recovery after MDMA exposure.
  • To evaluate the impact of different dextromethorphan concentrations (therapeutic vs. saturated) on MDMA's inhibitory effects.

Main Methods:

  • Thirty-two rats were divided into two groups based on dextromethorphan concentration (2 µM or 300 µM).
  • Each group was further divided into subgroups, with three receiving a single MDMA dose (1 mg/kg) at varying intervals before liver perfusion (1 hour, 1 week, 1 month).
  • A control subgroup received no MDMA treatment.

Main Results:

  • Using therapeutic dextromethorphan concentrations, a significant decrease in the metabolic ratio was observed only in the 1-hour MDMA treatment group compared to controls.
  • When using saturated dextromethorphan concentrations, a reduction in the mean metabolic ratio was noted across all MDMA treatment groups (p-value < 0.05).

Conclusions:

  • CYP2D6 enzyme behavior and recovery kinetics can differ significantly based on whether therapeutic or saturated probe concentrations are used.
  • The observed duality in metabolic behavior suggests that the metabolite's dependence on the enzymatic pathway influences enzyme recovery.
  • MDMA's inhibitory effect on CYP2D6 is concentration-dependent and influenced by the probe substrate used.