Fig. 1. Acute subjective effects of 125 mg MDMA, 125 mg S-MDMA, 125 mg R-MDMA, and 250 mg R-MDMA on the Visual Analog Scale (VAS).

S-MDMA produced overall stronger subjective responses than MDMA, with significant differences in “bad drug effects,” “alteration of vision,” and “audio-visual synesthesia.” R-MDMA at both doses produced overall lower subjective effects than MDMA, with significant differences in “drug high,” “happy,” “content,” “talkative,” “open,” “trust,” and “I feel close to others.” The substances were administered at t = 0 h. The data are expressed as the mean ± SEM percentage of maximally possible scores in 24 participants. The corresponding maximal responses and statistics are shown in Table 1.