The disposition into hair of new designer drugs; methylone, MBDB and methcathinone.

The disposition into hair of methylone and other new designer drugs, methcathinone and MBDB, was studied with the animal model. Moreover, the incorporation rates of these drugs were compared with those of their related eight compounds previously studied in order to evaluate their incorporation tendency into hair and the usefulness of hair specimens for the retrospective confirmation of the use of these drugs. When the ratio of hair concentration to AUC in plasma ([Hair]/AUC) was represented as an index of the incorporation rate of drugs into hair, the [Hair]/AUC of methylone was 14 times higher than that of methcathinone. It might support earlier findings that the methylenedioxy group on the benzene ring leads to considerably higher incorporation rates. However, [Hair]/AUC of methylone was five-sevenths times lower in comparison with that of MDMA. This suggested that the beta-carbonyl group leads to lower incorporation rates. Although methylone has both groups in its structure, the positive effect of the methylenedioxy group may be stronger than the negative effect of the beta-carbonyl group. On the other hand, the [Hair]/AUC of MBDB, which has methylenedioxyphenyl-2-butanamine structure, was higher than that of MDMA while that of methcathinone, having beta-ketone in its structure, was extremely low. In conclusion, as with MA and MDMA, the incorporation tendency of methylone and MBDB (except for methcathinone) into hair is relatively high, and a hair sample would be a good specimen for the confirmation of retrospective use of these drugs.