MDMA: interactions

MDMA raises extracellular serotonin by reversing transporter flux, pushing serotonin out of neurons into the synapse [1]. The risk of serotonin syndrome rises with higher MDMA doses [1]. As with serotonin syndrome generally, the result is a triad of altered mental status, autonomic instability, and neuromuscular abnormality [2], and it is described as potentially life-threatening [2]. SSRIs have been shown to block MDMA's effects in animal models, demonstrating a direct pharmacological interaction between SSRIs and MDMA [1].

MDMA and its metabolites also inhibit cytochrome P450 enzymes, which can slow the clearance of MDMA itself and of other drugs taken with it [1].

Recreational MDMA use is typically polydrug use, and mixing drugs this way carries drug-drug interaction risks described as extremely dangerous [1]. Part of that risk is invisible: ecstasy tablets frequently contain substances other than MDMA — methamphetamine, MDA, ketamine, cathinones, or opioids including fentanyl analogues — so a person combining "MDMA" with something else may unknowingly be combining that something else with an opioid they never intended to take [3]. MDMA already raises heart rate and blood pressure on its own [3]; as with sympathomimetic drugs generally, severe sympathomimetic toxicity can include ischemia, hemorrhage, seizures, and cardiovascular collapse [4].

References

1. Dark Classics in Chemical Neuroscience: 3,4-Methylenedioxymethamphetamine (MDMA) — NIH / ACS Chemical Neuroscience
2. Serotonin Syndrome — StatPearls (NCBI Bookshelf)
3. 3,4-Methylenedioxymethamphetamine (MDMA) — Drug Enforcement Administration (DEA) Diversion Control Division
4. Sympathomimetic Toxicity — StatPearls (NCBI Bookshelf)