HPLC-MS/MS stereoselective determination and quantification of MDMA and its phase-1 metabolite in human oral fluid samples: estimation of consumption time

3,4-Methylenedioxymethamphetamine (MDMA), commonly known as Ecstasy, is a psychoactive substance used for recreational purposes. This study used a stereoselective method based on high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC-MS/MS) to quantify MDMA and 3,4-methylenedioxyamphetamine (MDA) enantiomers in human oral fluid (OF). Samples were collected during a clinical trial and roadside police checks. The enantiomer concentrations were determined in 161 OF samples. Pharmacokinetic data showed that the S-(+)-enantiomer of MDMA was eliminated faster than the R-(-)-enantiomer, with half-lives of 3.3 hours and 4.8 hours, respectively. Peak concentrations for both enantiomers were reached within 1.75 hours post-administration. For MDA, the 2nd-enantiomer was eliminated more quickly, with a half-life of 9.6 hours compared to 23.8 hours for the 1st-enantiomer. The analysis of the MDMA R/S enantiomer ratio revealed a gradual increase over time, suggesting the possibility of estimating the time since ingestion. In samples collected during roadside checks, 54.5% of cases had an R/S ratio greater than 1.5, which might indicate consumption within the previous 24 hours. In conclusion, OF proved to be a promising non-invasive matrix for the detection of MDMA and MDA. The stereoselective analysis provided useful information for estimating the time of substance intake, especially in forensic contexts such as Driving Under the Influence of Drugs (DUID) cases.