Effects of the psychedelic amphetamine MDA (3, 4-methylenedioxyamphetamine) in healthy volunteers

MDA (3,4-methylenedioxyamphetamine) is an illicit drug historically used both experimentally in psychotherapy and nonmedically, and it remains encountered in contemporary drug markets where it is sometimes sold as "ecstasy." Prior work and user reports suggest MDA shares the socio-emotional, entactogen-like properties attributed to MDMA while also showing pharmacology that overlaps with classical psychedelics (notably 5-HT2A receptor agonism) and with psychostimulants (monoamine release). Controlled human data on MDA are sparse and the pharmacokinetics of orally administered MDA in humans had not been characterised in modern studies. Baggott and colleagues set out to address these gaps by conducting a double-blind, placebo-controlled, within-subjects laboratory study administering 1.4 mg/kg oral racemic MDA to healthy volunteers. The investigators measured physiological, endocrine, subjective (including psychedelic-like) and pharmacokinetic outcomes, and compared findings to data from prior, methodologically similar placebo-controlled studies of 1.5 mg/kg oral racemic MDMA to place MDA effects in context.

The study used a double-blind, placebo-controlled, within-subjects crossover design conducted at the UCSF Clinical Research Center. Participants were admitted for a single three-evening hospital stay with extensive safety monitoring from pre-dosing until resolution of drug effects, and a follow-up visit two weeks after discharge. Regulatory approvals and permissions from institutional and national bodies were obtained. For comparisons to MDMA, the investigators used data from two earlier placebo-controlled studies of 1.5 mg/kg oral racemic MDMA; those MDMA studies were described as methodologically comparable. Twelve healthy participants completed the MDA study. Eligibility included prior self-reported use of MDA alone or both MDMA and a classical serotonergic psychedelic, absence of DSM-IV drug dependence (except nicotine or caffeine), normal physical and laboratory screening (history and physical, EKG, liver panel, blood chemistry), and pregnancy and drug toxicology testing before dosing. Participants were asked to use effective contraception and to abstain from nicotine during the stay and from caffeine starting 10 hours before dosing. Racemic MDA was synthesised by the investigators and its identity and purity verified; dosing was 1.4 mg/kg given in a gelatin capsule after a two-hour fast. Placebo was lactose in an identical capsule. Dosing sessions (MDA and placebo) were scheduled on consecutive days. Because of this schedule, pharmacokinetic analyses excluded second-session placebo samples except where they could be used as scheduled late samples from the previous session. Outcome measures included repeated self-report instruments, physiological monitoring, endocrine assays, and pharmacokinetic sampling. Subjective measures comprised the 66-item Altered States of Consciousness (ASC) scale (translated from German and administered 8 h post-dose to retrospectively rate peak effects), a set of visual analog scales (VAS) administered repeatedly up to 8 h to track time course (covering general drug effects, entactogen-like items, and psychedelic-like items), the Affect Valuation Index (AVI) and the Interpersonal Adjectives Scale–Revised (IASR) administered pre-dose and at 2.5 h. Heart rate and blood pressure were measured hourly until 8 h (6 h for MDMA comparison data). Blood for prolactin and cortisol was sampled before and at 2 and 3 h post-dose. Pharmacokinetic samples were taken pre-dose and at 1, 2, 4, 6, 8, 12, 26 and 30 h; concentrations of MDA and its metabolite 4-hydroxy-3-methoxyamphetamine (HMA) were measured by two-dimensional GC/MS with an expanded dynamic range (MDA: 1–400 µg/L; HMA: 2.5–400 µg/L). Statistical analyses used mixed-effects models in R with drug condition as a fixed effect and participant as a random effect, two-tailed testing at the 0.05 level. Repeated measures were baseline-corrected and summarised as maximum effect (Emax) or area under the effect curve (AUC) before analysis; pairwise contrasts were corrected for multiple comparisons and were limited to within-study comparisons (MDA vs its placebo; MDMA vs its placebo). Pharmacokinetic parameters were estimated in NONMEM using noncompartmental linear trapezoidal calculations; half-life estimation was performed but the specific method reference is not clearly reported in the extracted text.

Twelve participants (mean age 27.8 ± 8 years; mean education 14.8 ± 2 years; mean weight 74.1 ± 9.2 kg) completed the study. Absolute MDA doses ranged from 83 to 128 mg. Checks for sequence effects (placebo and active sessions on consecutive days) did not indicate significant differences in physiological, endocrine, or self-report VAS measures attributable to dosing order, although pharmacokinetic sequence effects were present and were handled as described in the methods. On the Altered States of Consciousness (ASC) scale, both MDA and MDMA increased most ASC scales. The two drugs produced largely overlapping subjective profiles, but MDA produced more hallucinogen-like perceptual effects while MDMA produced more dysphoric effects. Measures of affect and social functioning (AVI and IASR) showed significant drug condition effects on Arousal (F3,68 = 5.30, p = 0.002) and a weaker effect on Valence (F3,68 = 2.35, p = 0.08), with both drugs having similar effects overall; however, only MDMA significantly increased Affiliation on the IASR. Visual analog scale analyses indicated partly overlapping profiles for MDA and MDMA. When Emax (peak) measures were examined the drugs largely did not differ, but AUC analyses—reflecting both magnitude and duration—showed greater scores for MDA on general drug effects, feelings of stimulation, and psychedelic-like items such as time distortion and closed-eye visual patterns. Duration differences were notable: MDA effects remained elevated at 6 h and 8 h, whereas MDMA effects had largely resolved by 6 h. For example, at 6 h the VAS item "Any drug effect" was 41.6 ± 7 units higher for MDA than for MDMA (z = 6.3, p < 0.001) and 46.4 ± 7 units higher for MDA than placebo (z = 6.7, p < 0.001). At 8 h "Any drug effect" was 35.6 ± 10 units higher for MDA than placebo (t = 3.7, p = 0.001). Physiologically, both drugs produced sympathomimetic effects. There were significant main effects of condition on baseline-corrected maximum heart rate (F3,22 = 17.1, p < 0.0001), diastolic blood pressure (F3,22 = 32.4, p < 0.0001), and systolic blood pressure (F3,22 = 61.7, p < 0.0001). Heart rate increased by 20 ± 3 bpm after MDA and by 30.6 ± 4.5 bpm after MDMA (difference p = 0.03). Peak systolic blood pressure rose similarly after MDA (33 ± 2 mmHg) and MDMA (31 ± 3 mmHg). There was a trend toward a larger diastolic increase after MDA (24 ± 2 mmHg) versus MDMA (19 ± 2 mmHg; p = 0.06). Endocrine measures showed that both MDA and MDMA elevated serum prolactin and cortisol. Prolactin increased by 16 ± 6 ng/mL after MDA and 29 ± 6 ng/mL after MDMA versus placebo (F3,25 = 13.0, p < 0.0001), with a nonsignificant trend for higher peak prolactin after MDMA (p = 0.07). Cortisol rose by 16 ± 1 µg/dL after MDA and 13 ± 2 µg/dL after MDMA versus placebo (F3,24 = 43.1, p < 0.0001). Pharmacokinetic results for MDA were: Cmax 229 ± 39 µg/L and AUC0–∞ 3,636 ± 958 h•µg/L. For the metabolite HMA, Cmax was 92 ± 61 µg/L and AUC0–∞ was 1,544 ± 741 h•µg/L. Elimination half-lives were 10.9 ± 4 h for MDA and 14.1 ± 3 h for HMA. Total MDA clearance/F was reported as 30,267 ± 8,214 mL/min. Considerable between-subject variability was observed in HMA formation, with HMA Cmax and AUC varying roughly seven-fold and four-fold between individuals, respectively.

Baggott and colleagues present the first controlled human study of MDA in over 35 years and the first modern measurement of MDA pharmacokinetics in humans. They interpret the results as indicating that MDA produces a blend of MDMA-like entactogen effects, classical psychedelic-like effects, and stimulant-like sympathomimetic effects. Psychedelic-like phenomena observed after MDA included complex closed-eye imagery, synesthesia and spiritual-type experiences; the authors suggest these features may reflect MDA's greater efficacy at stimulating 5-HT2A receptors compared with MDMA. The investigators note qualitative differences between the drugs: MDA appeared to elicit a more introverted, emotionally intense prosocial state, whereas MDMA promoted a more extraverted, gregarious prosociality. Both drugs produced significant increases in heart rate and blood pressure comparable to those seen with psychostimulants; these cardiovascular effects were well tolerated in healthy volunteers but could pose risks for people with cardiovascular disease. Pharmacokinetically, MDA and MDMA were broadly similar at the doses studied, although MDA showed a possibly longer elimination half-life, which may contribute to the longer subjective duration observed; alternatively, differences in pharmacodynamics (greater direct 5-HT2A agonism for MDA versus reliance on releasable monoamines for MDMA) could explain the duration differences. The authors acknowledge several limitations: dosing sessions were on consecutive days, which may have allowed residual next-day MDA effects to influence some placebo measures; comparisons with MDMA came from separate studies, reducing power for direct drug–drug contrasts; the use of racemic compounds rather than isolated enantiomers limits mechanistic inference; and the modest sample size, low number of female participants, and single dose level constrain the generalisability and full characterisation of MDA pharmacokinetics. Despite these caveats, the study confirms that MDA has significant MDMA-like and LSD-like subjective effects and suggests that further mechanistic work, particularly studies of individual enantiomers, could help disentangle therapeutic versus other psychoactive properties.