Discontinuation of medications classified as reuptake inhibitors affects treatment response of MDMA-assisted psychotherapy

Feduccia and colleagues frame the study within ongoing investigations of MDMA-assisted psychotherapy as a treatment for post-traumatic stress disorder (PTSD). Earlier phase 2 trials demonstrated large between-group reductions in CAPS‑IV PTSD severity for participants receiving active MDMA (75–125 mg) plus manualised psychotherapy compared to control doses, and MDMA is known to increase synaptic serotonin, norepinephrine, and dopamine via reversal of transporter proteins (SERT, NET, DAT). Because many commonly prescribed antidepressant medications for PTSD (SSRIs, SNRIs, NRIs, NDRIs) act on the same reuptake transporters, prior studies have shown that co-administration or recent use of such drugs can attenuate MDMA's subjective and physiological effects, and participants in the phase 2 trials were required to taper off psychiatric medications before MDMA sessions to minimise interactions and withdrawal effects. This paper pools data from four phase 2 randomized, double-blind trials to explore whether recent tapering off medications classified as reuptake inhibitors affected clinical and physiological responses to active MDMA-assisted psychotherapy. The investigators compared PTSD severity (CAPS‑IV), depression symptoms (BDI‑II), and peak vital signs during MDMA sessions between participants who had tapered off reuptake inhibitors prior to blinded sessions (taper group) and those who had not been taking such medications at screening (non-taper group). The intent was to assess whether recent exposure to reuptake inhibitors blunts treatment response to MDMA-assisted psychotherapy and to characterise any related physiological differences.

Using pooled data from four randomized, double-blind Phase II trials conducted in the USA, Canada, and Israel between December 2010 and March 2017, the study analysed only participants who were randomised to receive active doses of MDMA (75 mg, 100 mg, or 125 mg) during the blinded segment. The trials shared a manualised psychotherapy format that included preparatory sessions, two 8‑hour blinded MDMA-assisted psychotherapy sessions spaced 3–5 weeks apart (each with an optional supplemental half-dose 1.5–2.5 hours after the initial dose), and three non-drug integrative sessions afterwards. The primary outcome assessment occurred 1–2 months after the second blinded session and was administered by independent blinded raters. Participants were adults with chronic PTSD (symptoms >6 months) meeting CAPS‑IV severity thresholds (≥50 in most studies, ≥60 in one study). Psychiatric medications were tapered and discontinued prior to experimental sessions according to protocol guidance (medications to be discontinued at least five half-lives before MDMA), though the extracted text notes that exact taper start dates and taper durations were not collected. The investigators divided the analytic sample into a taper group (participants who had tapered off medications classified as reuptake inhibitors prior to the blinded sessions) and a non-taper group (participants who had not been taking reuptake inhibitors at screening; they may have tapered other drug classes). Primary analyses consisted of repeated measures ANOVA with time (baseline and primary endpoint) as the within-subject factor and group (taper vs non-taper) as the between-subject factor for CAPS‑IV total scores and BDI‑II total scores; Bonferroni post hoc tests were applied when main effects were detected. Independent-samples t tests compared peak (maximum) vital signs across the two MDMA sessions between groups. Pearson correlations explored relationships between days abstinent from reuptake inhibitors (stop date to first MDMA session), change in CAPS‑IV scores, and average peak vital signs. Baseline group comparisons used chi-squared tests or independent t tests as appropriate. All available data at each endpoint were used and missing data were not imputed.

Fifty participants randomised to active MDMA doses comprised the analytic sample, of whom 16 were classified in the taper group and 34 in the non-taper group; one participant in the non-taper group dropped out before the primary endpoint. The extracted text does not clearly report mean ages for each group. Most participants tapered one reuptake inhibitor (n = 12), with a few tapering two (n = 3) or three (n = 1) drugs. The average number of days from medication cessation to the first MDMA session was 25.1 (SD 17.7), range 4–70 days; taper start dates and taper durations were not recorded. For the primary outcome, CAPS‑IV total severity, there was a significant time × group interaction (F(1,47) = 5.86, p = 0.019). The mean change from baseline to primary endpoint was −41.1 (SD 19.86) for the non-taper group (n = 33 at endpoint) and −22.6 (SD 33.80) for the taper group (n = 16). At the primary endpoint, the non-taper group had significantly lower CAPS‑IV scores (mean 45.7, SD 27.17) than the taper group (mean 70.25, SD 33.60), p = 0.009. A greater proportion of participants in the non-taper group no longer met PTSD diagnostic criteria at the primary endpoint (63.6%) compared to the taper group (25.0%); chi-squared X2(1) = 6.437, p = 0.011. There was no significant correlation between days abstinent from reuptake inhibitors and change in CAPS‑IV scores (r = 0.13, p = 0.633). Depression symptoms measured by BDI‑II also showed a significant time × group interaction (F(1,47) = 4.88, p = 0.032). The non-taper group had lower BDI‑II scores at the primary endpoint (mean 12.4, SD 10.17) than the taper group (mean 22.6, SD 16.69), p = 0.010. Mean changes from baseline to endpoint were −17.2 (SD 11.48) for non-taper and −8.3 (SD 16.70) for taper. Regarding physiological responses during MDMA sessions, the non-taper group exhibited higher peak blood pressure values: systolic mean 152.5 (SD 17.60) versus 144.5 (SD 18.54) in the taper group (p = 0.043), and diastolic mean 93.1 (SD 11.74) versus 87.8 (SD 9.78) (p = 0.032). No significant between-group differences were found for peak heart rate or body temperature, nor were there differences at pre-dose or session endpoint measurements. Days abstinent prior to the first MDMA session positively correlated with average maximum body temperature during sessions (r = 0.381, p = 0.032); correlations with systolic (r = 0.326, p = 0.069) and diastolic blood pressure (r = 0.307, p = 0.088) trended in the same direction but did not reach conventional significance.

Feduccia and colleagues interpret the pooled results as evidence that recent prior use and tapering of medications targeting monoamine reuptake transporters was associated with attenuated clinical and physiological responses to MDMA-assisted psychotherapy in these Phase II samples. Participants who had tapered reuptake inhibitors showed smaller reductions in PTSD severity and depression scores and were less likely to no longer meet PTSD diagnostic criteria at the primary endpoint, while also demonstrating smaller MDMA-induced rises in systolic and diastolic blood pressure compared with participants who had not recently taken such medications. The authors propose biological explanations centred on transporter and receptor adaptations induced by chronic reuptake inhibitor treatment. Long-term SSRI use can downregulate SERT expression and alter other serotonin receptor function (for example, diminished 5-HT1A-mediated hormonal responses and reduced sensitivity of 5-HT2A/5-HT4 receptors), which could blunt MDMA-stimulated efflux of monoamines and downstream release of oxytocin and ACTH—mechanisms thought to contribute to MDMA's subjective and therapeutic effects. Reduced extracellular monoamine increases after MDMA would also be consistent with the smaller blood pressure elevations seen in the taper group. The authors note, however, that body temperature and heart rate did not differ between groups, and that precise contribution of each monoamine to physiological effects remains uncertain. Withdrawal or discontinuation syndrome is offered as an alternative or complementary explanation. Participants in the taper group often discontinued multiple medications and may have experienced withdrawal symptoms that either interfered with therapeutic engagement during MDMA sessions or overlapped with PTSD and depression measures. Nonetheless, baseline CAPS‑IV and BDI‑II scores were equivalent between groups, and the placebo/control psychotherapy arm (reported in supplemental material) did not show taper-related differences, which the authors interpret as evidence that discontinuation effects alone do not fully account for the observed differences in MDMA response. The lack of a relationship between days abstinent and PTSD outcome is acknowledged, with the authors suggesting that the small sample size, heterogeneity of medications tapered, and variable abstinence intervals (average 25 days, range 4–70) may have obscured any temporal effects. Key limitations are highlighted: small and unequal group sizes (taper n = 16, non-taper n = 34), pooling across multiple sites, heterogeneity in the specific medications and number of drugs tapered, and absence of recorded taper durations or start dates. The taper group also discontinued other psychiatric medications which could have influenced outcomes, and the possibility that the taper group represented a more severe clinical burden is acknowledged though not evident in baseline measures. The authors conclude that these preliminary findings warrant attention in ongoing and future trials, and that phase 3 data with larger samples will be needed to characterise effects of discontinuation of specific medications more precisely. Finally, the investigators suggest a practical implication: if confirmed, allowing substantially longer tapering and abstinence periods off reuptake inhibitors prior to MDMA-assisted psychotherapy might increase treatment efficacy, a consideration for clinical practice should MDMA-assisted psychotherapy gain regulatory approval.