Safety pharmacology of acute MDMA administration in healthy subjects

MDMA (3,4-methylenedioxymethamphetamine; ecstasy) is investigated clinically as an adjunct to psychotherapy, notably for post‑traumatic stress disorder, but broader clinical adoption depends on robust evidence of safety as well as efficacy. Earlier experimental studies have described MDMA’s subjective and physiological effects, but most were small (n = 6–30) and not expressly designed to quantify adverse events that occur at low frequency. The authors note a need for larger, standardised data sets to characterise acute and subacute safety in healthy volunteers prior to wider patient trials. Using pooled data from nine Phase I double‑blind, placebo‑controlled, crossover studies conducted at a single centre, the investigators aimed to describe the safety pharmacology of single oral doses of MDMA (75 mg and 125 mg). Primary objectives were to characterise the time course and magnitude of subjective effects, cardiovascular and thermogenic responses during the acute MDMA response (0–6 h), subacute adverse effects up to 24 h, and laboratory indices of liver and kidney function at end‑of‑study follow‑up. The analysis also tested dose and sex as moderators of these responses and reported plasma MDMA concentrations alongside clinical measures.

The analysis pooled data from nine Phase I, double‑blind, placebo‑controlled, crossover studies performed at the University Hospital Basel. In total 166 psychiatrically and physically screened healthy European/Caucasian subjects aged 18–45 years (mean 24.5 ± 4 years) were included. The core focus was on single‑dose administrations of MDMA alone: 30 subjects (15 men, 15 women) received a single 75 mg dose, and 136 subjects received a single 125 mg dose (24 of these received it once; 112 received two 125 mg administrations on separate occasions, once alone and once following a pretreatment in other study arms). The pooled data therefore comprised 166 administrations of MDMA alone and 112 administrations with a pretreatment (278 MDMA administrations in total), but the present report emphasised effects of MDMA without pretreatment. Washout periods were at least seven days. Exclusion criteria included psychiatric disorder, significant physical illness, more than five lifetime illicit drug uses (except past cannabis), recent illicit drug use, and positive urine drug tests. MDMA hydrochloride was administered orally as gelatin capsules of 75 mg or 125 mg (fixed doses, not adjusted for body weight or sex). Dose per body weight averaged 1.7 ± 0.4 mg/kg overall; for 125 mg the mean was 1.7 ± 0.2 mg/kg for men and 2.1 ± 0.3 mg/kg for women. Pharmacodynamic measures comprised repeated visual analogue scales (VAS; 0–100 mm) for 'any drug effect', 'good drug effect' and 'bad drug effect' at baseline and multiple time points up to 6 h post‑dose. Onset, peak and duration of subjective response were calculated from the 'any drug effect' curve using a 10% of peak threshold. Cardiovascular monitoring included duplicated, averaged oscillometric blood pressure and heart rate measurements after at least 10 min rest; core (tympanic) temperature was also recorded. Acute and subacute adverse effects were assessed with a 66‑item List of Complaints administered before dosing, 3–6 h after dosing (acute) and 24 h after dosing (subacute). Plasma MDMA concentrations were measured and Cmax and AUC0–6h were derived. Blood chemistry and cell counts were obtained at screening and at the end‑of‑study (EOS) visit; the EOS sampling occurred a mean 29 ± 22 days after the last MDMA administration, with screening to EOS spanning 88 ± 50 days. Statistical analyses used repeated‑measures ANOVA with drug (MDMA vs placebo) as within‑subjects factor and dose (75 vs 125 mg) and sex as between‑subjects factors; Tukey post hoc tests, Fisher’s exact tests for proportions, paired t‑tests for laboratory comparisons, and covariate analyses using mg/kg dose and plasma concentrations were also employed. Significance was set at p < 0.05.

Sample characteristics: 166 healthy subjects (approximately equal numbers of men and women) received MDMA in the pooled data set. Thirty subjects received 75 mg once; 136 received 125 mg (24 once; 112 received two 125 mg administrations at separate visits). Fifty‑nine subjects had prior limited illicit‑drug experience; 34 had previously used MDMA 1–4 times. Subjective effects and time course: The average onset of any subjective drug effect was 33 ± 24 minutes, peak occurred at 1.6 ± 0.8 h, and mean duration (onset to offset using a 10% of peak threshold) was 4.2 ± 1.3 h (range 1.4–8.2 h). Retrospective EOS ratings closely matched this duration (mean 4.0 ± 2.9 h). MDMA significantly increased 'any drug effect' and 'good drug effect' VAS scores versus placebo; the 125 mg dose produced larger 'any' and 'good' effect ratings than 75 mg. 'Bad drug effect' ratings were increased by MDMA but were not dose dependent; women reported greater 'bad drug effect' ratings than men. This sex difference persisted after covarying for mg/kg dose (F1,162 = 20.0; p < 0.001) and after adjusting for peak plasma concentrations (F1,162 = 21.5; p < 0.001). Cardiovascular and temperature effects: MDMA acutely increased systolic and diastolic blood pressure, heart rate and tympanic temperature. Peak effects occurred at roughly 1.7 h for systolic blood pressure, 2.0 h for heart rate and 2.4 h for temperature. A dose‑response effect was significant for blood pressure but not for heart rate or temperature. Across 166 administrations of MDMA alone, 54 subjects (33%) reached systolic blood pressure >160 mmHg and seven subjects (4%) exceeded 180 mmHg; the proportion with systolic >160 mmHg was significantly greater after 125 mg than 75 mg (p < 0.01). Forty‑eight subjects (29%) developed tachycardia (>100 beats/min), with a higher proportion after 125 mg versus 75 mg (p < 0.05). Tympanic temperature exceeded 38°C in 32 subjects (19%), up to a maximum observed temperature of 39.1°C; the >38°C proportion was greater after 125 mg than 75 mg (p < 0.01). No incidents of hyperpyrexia (>40°C) or hypertensive urgencies were observed. When dose was normalised by body weight or plasma MDMA concentration, men showed greater increases in systolic blood pressure than women (dose‑normalised: F1,164 = 6.08, p < 0.05; plasma‑corrected: F1,164 = 8.28, p < 0.01). Adverse effects and safety events: Acute and subacute total scores on the List of Complaints were higher after MDMA than placebo, and the 125 mg dose produced larger increases than 75 mg. Women had higher acute (8.8 ± 5.9 vs 6.4 ± 6.8) and subacute (5.4 ± 5.5 vs 3.0 ± 5.0) complaint scores than men; these differences remained after correction for mg/kg dose and plasma levels. The most frequent acute complaints after MDMA included dry mouth, lack of appetite, difficulty concentrating, cold feet, sweating, bruxism, restless legs, dizziness and hot flushes. Common subacute complaints at 24 h included headache, lack of energy, lack of appetite, dry mouth, difficulty concentrating and bruxism. Acute anxiety was reported by nine subjects (6%) after 125 mg and by none after 75 mg. No serious adverse events were reported. Between 24 h and 7–14 days post‑dose, a range of mostly mild complaints was reported at low frequencies and not significantly above placebo. Flashbacks were reported by 12 subjects (9% of those asked), occurring 8–50 h after dosing; no persistent perceptual disorders were identified in this controlled setting. Plasma pharmacokinetics and laboratory measures: Cmax averaged 224.1 ng/mL after 125 mg and 124.5 ng/mL after 75 mg; the dose‑normalised Cmax differed significantly overall (F1,161 = 4.19; p < 0.05), driven by a significant change in women, indicating non‑linear pharmacokinetics over this dose range. At the same 125 mg dose women had on average 1.29‑fold higher Cmax and 1.26‑fold higher AUC0–6h than men. Paired comparisons of screening and EOS blood chemistry showed no significant changes in plasma creatinine, estimated glomerular filtration rate, or liver enzymes (AST, ALT, GGT) approximately one month after MDMA exposure. Red blood cell counts and haemoglobin decreased while platelet counts increased over the study period; the authors attribute these changes to cumulative blood sampling for pharmacokinetic analysis (400–600 mL) rather than to MDMA. Red cell and haemoglobin reductions were more pronounced in women (F1,159 = 8.12, p < 0.01 and F1,159 = 12.9, p < 0.001, respectively). Subject attitudes: Of 141 subjects queried at EOS, 67% reported an overall positive MDMA experience. Nineteen per cent stated they would not take MDMA again under any circumstances; 47% would avoid recreational use but might participate in another controlled study; 34% might consider recreational use if identity, purity and dose were known.

Using pooled placebo‑controlled Phase I data, Vizeli and colleagues report that single doses of MDMA produced predominantly positive acute subjective effects alongside measurable sympathomimetic activation and a set of attenuated, mostly transient adverse effects. The typical subjective time course was brief relative to MDMA’s plasma persistence: onset at about 33 minutes, peak at 1.6 hours and mean duration around 4.2 hours. The authors interpret the shorter subjective duration despite ongoing plasma exposure as reflecting acute pharmacological tolerance. Cardiovascular and thermogenic effects were dose dependent for blood pressure and resulted in clinically relevant elevations in a substantial minority of healthy participants: about one‑third reached systolic blood pressure >160 mmHg and nearly one‑third developed tachycardia >100 beats/min; body temperature exceeded 38°C in about 19% with a maximum observed of 39.1°C. No hyperpyrexia (>40°C) or hypertensive urgencies occurred in the controlled, rested setting. The investigators caution that these cardiovascular responses could represent meaningful risks in older patients or those with cardiovascular disease. The pooled analysis also identified sex differences: women experienced more negative subjective and adverse effects than men even after adjusting for mg/kg dosing and plasma levels, while dose‑normalised blood pressure increases were larger in men. Pharmacokinetically, the 125 mg dose produced disproportionally higher Cmax and AUC than 75 mg, with nonlinearity statistically evident particularly in women; at a fixed 125 mg dose women had about 1.3‑fold higher Cmax than men, largely attributable to lower body weight. On laboratory safety, no average adverse effects on liver or renal function were found at the EOS visit approximately one month after dosing, and the observed decreases in haemoglobin and red cells were attributed to cumulative blood draws. The authors note important limitations: the sample comprised psychiatrically and physically healthy, mostly young adults so findings may not generalise to patients or older people with cardiovascular risk; hyponatraemia and formal neurocognitive or long‑term neurotoxicity assessments were not performed; end‑of‑study laboratory sampling was delayed and could miss transient changes; and the pooled sample remained too small to exclude rare adverse events (<0.1–1%). Finally, the investigators discuss implications for dosing in therapeutic contexts: because women showed similar adverse‑effect scores on 75 mg as men on 125 mg, but higher 'good effect' ratings at 125 mg, they suggest considering a fixed 100 mg dose in women as roughly comparable to 125 mg in men. The authors emphasise that while single‑dose MDMA was overall well tolerated in a controlled clinical environment, cardiovascular stimulation is dose dependent and should be carefully considered when treating patients with cardiovascular disease, and that risks in psychiatric patient populations remain to be studied further.

In healthy, psychiatrically screened adults in a controlled clinical setting, single‑dose oral MDMA (75 or 125 mg) produced predominantly positive acute subjective effects and was not associated with serious adverse events. MDMA induced dose‑dependent cardiovascular stimulation and modest thermogenic effects; clinically relevant hypertension, tachycardia and temperatures >38°C occurred in notable minorities, more commonly after 125 mg. Women reported more subjective negative and adverse effects than men even after adjusting for dose per body weight and plasma levels; women also showed higher plasma exposure at the same fixed dose. No lasting changes in liver or kidney laboratory indices were observed at the end‑of‑study visit about one month after dosing. The authors conclude these safety data support further clinical research of MDMA in controlled psychotherapy settings but caution that cardiovascular risks—particularly in patients with pre‑existing cardiovascular disease—and safety in psychiatric patient populations require additional study.