Pharmacology of MDMA in humans

De and colleagues situate MDMA (3,4-methylenedioxymethamphetamine) as an amphetamine derivative with both stimulant and serotonergic (hallucinogenic-like) actions that distinguish it from classical amphetamines. Earlier human reports have documented prominent sympathomimetic cardiovascular and autonomic effects (increased blood pressure, pulse, mydriasis, diaphoresis, jaw clenching) together with subjective confusion and modest psychomotor impairment. Metabolically, MDMA undergoes N‑demethylation to MDA and subsequent O‑demethylenation and O‑methylation steps producing HMMA and HMA; however, plasma data and urinary quantitative recoveries for these metabolites remain limited. This paper reports experimental data from a new clinical trial administering a single oral 100 mg dose of MDMA to healthy volunteers and compares those findings with prior controlled doses (50, 75, 125, and 150 mg) examined in the authors’ earlier pilot and controlled studies. The study aims to characterise physiologic, psychomotor, neuroendocrine, and pharmacokinetic effects of MDMA and its main metabolites across the recreational dose range, including examination of dose–response patterns and possible nonlinear kinetics.

The investigators conducted randomized, double‑blind, placebo‑controlled, crossover clinical trials in a total of 27 healthy male recreational MDMA users. Inclusion characteristics reported that participants had used MDMA on 5–50 prior occasions (mean about 25), had previous exposure to cannabis, cocaine, and methamphetamine, and did not meet DSM‑IV criteria for substance abuse or dependence (except nicotine). Different single oral d,l‑MDMA doses were given across studies: 50 mg (n = 2), 75 mg (n = 10), 100 mg (n = 13), 125 mg (n = 8), and 150 mg (n = 2); eight subjects received both 75 mg and 125 mg in one crossover study. All participants provided informed consent and studies had ethical and regulatory approvals. Physiologic monitoring included noninvasive heart rate, systolic and diastolic blood pressure, oral temperature, pupillary diameter and continuous ECG. Psychomotor assessment used a battery comprising simple reaction time (Vienna Reaction Unit), a computerized Digit Symbol Substitution Test (DSST), and the Maddox‑wing device to detect ocular alignment changes (esophoria/exophoria). Blood sampling was performed via an indwelling catheter with timed collections for MDMA and metabolites (MDA, HMMA, HMA) at 0, 15, 30, 45, 60, 90 min, and 2, 3, 4, 6, 8, 10, and 24 h. Hormone samples for cortisol and prolactin were taken at 0, 30, 60, 90 min, and 2, 3, 4, and 6 h. Plasma/serum were frozen at −20°C until assay. Drug assays for MDMA and metabolites used gas chromatography with nitrogen‑phosphorus detection or GC‑mass spectrometry with deuterated internal standards. Calibration ranges and limits of quantification for each analyte are reported; intra‑ and interday precision and accuracy metrics are provided. Cortisol and prolactin were measured by fluorescence polarisation immunoassay and microparticle enzyme immunoassay, respectively. Pharmacokinetic parameters derived included Cmax, tmax, AUC0‑24, AUCtotal, absorption and elimination half‑lives, calculated with PKCALC. Outcome data were expressed as change from baseline; when sample size allowed, repeated measures ANOVA with drug condition and time factors and Tukey post‑hoc tests were used. Statistical significance was set at p < 0.05.

Sample and dosing: Data were obtained from 27 male recreational MDMA users with the following subject‑dose counts: 50 mg (n = 2), 75 mg (n = 10), 100 mg (n = 13), 125 mg (n = 8), 150 mg (n = 2); eight subjects received both 75 mg and 125 mg in one study arm. Sympathomimetic and autonomic effects: Except at 50 mg, MDMA produced dose‑related increases in systolic and diastolic blood pressure, pulse rate, and pupillary diameter. At doses of 75 mg and above some participants met criteria for hypertension and sinus tachycardia. Mydriasis persisted longer than cardiovascular effects. Oral temperature followed a biphasic course with a small decrease at 1 h and slight increases at 2 and 4 h. Peak physiologic effects and concentrations typically occurred between 1 and 2 h and returned toward baseline by 4–6 h. Psychomotor and ocular findings: MDMA induced a slight dose‑dependent impairment on the DSST. Total reaction time showed a marginal, non‑statistically significant increase, mainly attributable to longer decision time rather than motor time. The Maddox‑wing test indicated esophoria at all active doses except 50 mg. Neuroendocrine effects: Plasma cortisol and prolactin rose significantly after MDMA compared with placebo. Reported peak differences for cortisol were: MDMA 125 vs placebo +17.3 µg/dl; MDMA 100 vs placebo +19.6 µg/dl; MDMA 75 vs placebo +13.4 µg/dl, with cortisol peaking at about 2 h. For prolactin the peak differences were: MDMA 125 vs placebo +17.4 ng/ml; MDMA 100 vs placebo +22.1 ng/ml; and MDMA 100 vs MDMA 75 +15.7 ng/ml; prolactin also peaked near 2 h. The authors note a plateau in hormonal responses between 100 and 125 mg. Pharmacokinetics and metabolites: For the 100 mg MDMA dose, tmax for MDMA was observed at about 2 h and plasma decline followed a monoexponential profile with a mean elimination half‑life of approximately 8–9 h. MDA appeared slowly, with a Cmax of about 13.1 ng/ml reached at 5–7 h after a 100 mg MDMA dose; the estimated MDA formation rate constant for the 100 mg dose was ~0.63 h−1 and MDA elimination half‑life around 25 h. HMMA and HMA plasma concentration profiles were similar to those of their precursors (MDMA and MDA, respectively). HMMA was identified as the major metabolite in plasma and urine; urinary recovery at 100 mg was roughly 13–14% for HMMA and about 24% for parent MDMA in 24 h. MDA represented a minor metabolite (about 8–9% of MDMA AUC) with low urinary recovery (~1%). The intermediate dihydroxy metabolites (HHMA, HHA) were not detected in plasma and only at very low levels in urine under the applied analytical conditions. Dose linearity observations: The authors observed a disproportionate increase in MDMA plasma concentrations after 150 mg in two volunteers, suggesting possible nonlinear pharmacokinetics, although they state this requires confirmation in studies specifically designed to evaluate nonlinearity.

De and colleagues interpret their results as confirmation that single oral MDMA doses in the recreational range (75–150 mg) produce marked sympathomimetic effects—hypertension, tachycardia—and pronounced mydriasis, consistent with prior human studies and with effects seen after related phenethylamines such as MDEA. They emphasise that temperature showed a biphasic pattern with a small early decrease followed by modest increases at 2–4 h; while laboratory increases in oral temperature were marginal, the authors note that environmental factors (crowded settings, high ambient temperature, physical activity) could convert these modest changes into clinically relevant hyperthermia in real‑world intoxications. On psychomotor function, the observed slight impairment on DSST and subjective reports of confusion and mental slowing are discussed as possibly attributable to the serotonergic/hallucinogenic profile of MDMA, in contrast with the performance enhancement typically seen with classical amphetamines. The differential effects across specific cognitive tests are suggested to reflect varying task complexity and attentional demands. Regarding neuroendocrine responses, the study documents significant cortisol and prolactin increases peaking around 2 h; the lack of large differences between 100 mg and 125 mg led the authors to propose a plateau effect for these hormonal responses. They acknowledge that multiple neurotransmitter systems (serotonergic, dopaminergic, noradrenergic) likely contribute to the endocrine changes. Pharmacokinetic conclusions highlight a tmax near 2 h and an elimination half‑life for MDMA of about 8–9 h at 100 mg, shorter than those reported for methamphetamine or amphetamine. The investigators present HMMA as the principal metabolite and note practical analytical challenges—in particular, HMMA detection often requires enzymatic hydrolysis and intermediate catechol metabolites (HHMA, HHA) were not observed in plasma under their assay conditions. The authors discuss evidence suggestive of nonlinear kinetics at higher doses and propose mechanisms such as metabolic saturation or metabolite–enzyme interactions; they caution that confirmation requires targeted study designs. Limitations and implications noted by the authors include the small numbers at the extreme doses (50 mg and 150 mg), potential overestimation of elimination half‑life for HMA due to sampling limited to 24 h, and analytical limitations for unstable intermediate metabolites. They conclude that, given the pharmacologic profile observed in controlled settings, MDMA use in hot, crowded, physically active environments could substantially increase the risk of life‑threatening toxicity.