MDMA (ecstasy) inhibition of MAO type A and type B: comparisons with fenfluramine and fluoxetine (Prozac).
E T Leonardi, Efrain C. Azmitia
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology July 1994 DOI: 10.1038/npp.1994.26 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | In vitro enzyme kinetics study Peer reviewed |
|---|---|
| Population | Rat brain homogenates |
| Interventions | MDMA fenfluramine fluoxetine |
| Measures | Ki, IC50 |
| Topics | MDMA |
| Key points | MDMA preferentially inhibits MAO-A (IC50 = 44 micromol/L) over MAO-B (IC50 = 370 micromol/L) in rat brain homogenates, which the authors state should increase extracellular serotonin. Fenfluramine's effects do not appear to involve MAO inhibition, and combining fluoxetine with MDMA at their IC50 values produced no greater MAO inhibition than either drug alone. |
Abstract
3,4-Methylenedioxymethamphetamine (MDMA), a serotonin (5-HT) neurotoxin, has been shown to promote the release of serotonin (5-HT) and block its reuptake. The increased buildup of extracellular 5-HT should normally be degraded by monoamine oxidase (MAO). The effects of both enantiomers of MDMA were examined on MAO-A and monoamine oxidase-B (MAO-B) activity in rat brain homogenates. Both enantiomers competitively inhibited 5-HT catabolism by rat brain MAO-A. The Ki of MDMA for MAO-A was 22 mumol/L. A mixed type of inhibition by MDMA was observed for phenethylamine catabolism by MAO-B for both optical antipodes. Logistical analysis of concentration response curves for MDMA inhibition of MAO-A and MAO-B show an IC50 of 44 mumol/L for inhibition of MAO-A by MDMA. The IC50 value of MDMA inhibition of MAO-B was 370 mumol/L, showing a selective potency for MAO-A inhibition. The MAO inhibitory properties of fenfluramine (FEN) and fluoxetine (FLUOX) were compared to those of MDMA. The rank order potency of these drugs for MAO-A inhibition was MDMA > FLUOX > FEN, whereas for MAO-B inhibition, FLUOX > MDMA > FEN. A combination of FLUOX and MDMA at their respective IC50 did not inhibit MAO activity more than either drug alone at equivalent concentrations. These results indicate that the actions of FEN do not appear to involve MAO inhibition. MDMA (ecstasy) produced a preferential inhibition of MAO-A (IC50 = 44 mumol/L), which should increase extracellular 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)