After a 40 mg oral dose of racemic MDMA (ecstasy) to eight men, the R-enantiomer reached higher and longer-lasting plasma levels than the S-enantiomer. The R-enantiomer's half-life was 5.8 hours versus 3.6 hours for S-MDMA, and its area under the curve was 2.4 times greater. More R-MDMA was excreted in urine (21.4% of dose) than S-MDMA (9.3%). The demethylated metabolite MDA appeared in smaller amounts, with S-MDA slightly exceeding R-MDA. Mathematical modeling of plasma enantiomer ratios over time suggests that analyzing stereochemical composition could help estimate time since drug intake for forensic purposes.
MDMA and its metabolites can stimulate release of the hormones vasopressin and oxytocin from rat hypothalamic tissue in the laboratory. The metabolite HMMA (4-hydroxy-3-methoxymethamphetamine) was the most potent, increasing basal vasopressin release more than twofold and oxytocin release by about 60% at a concentration of 10 nM. MDMA itself produced smaller increases. The effect on vasopressin release was consistently greater than on oxytocin. These findings suggest that MDMA-induced hyponatraemia (low blood sodium) may result from excessive vasopressin secretion triggered by the drug or its breakdown products.