High performance liquid chromatographic assays of the illicit designer drug "Ecstasy", a modified amphetamine, with applications to stability, partitioning and plasma protein binding.

Specific, sensitive, reverse-phase high-performance liquid chromatographic (HPLC) assays of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) have been devised with analytical sensitivities as low as 2.7 ng/ml of plasma for MDMA and 1.6 ng/ml for MDA, using spectrophotometric detection at 280 nm. The assays were used to determine some properties of MDMA and MDA. Both drugs were stable in aqueous 1 M HCl, and 1 M NaOH solutions at room temperature. The half-life for MDMA was 6.6 h and for MDA was 7.1 h under the extreme conditions of 90 degrees C and 6 M HCl. MDMA and MDA were highly stable for 28 h in plasma at 25 degrees and 39 degrees C. The concentrations of the drugs were unchanged in frozen plasma after 47 days. The apparent red blood cell-plasma partition coefficient determined from assayed concentrations of the drugs in plasma and erythrocytes was 1.45 for both MDMA and MDA. An equation is presented to correct drug concentration in erythrocytes for the trapped equilibrated plasma/buffer in the packed red blood cells. The fraction of MDMA and MDA bound to dog plasma proteins was determined by several methods and it is 0.34-0.40 for both drugs. The extent of protein binding was independent of the drugs' concentration.