Determination of the stereoisomeric distribution of R-(−)- and S-(+)-methamphetamine in Thai pills in the legal context of “not inconsiderable quantities"

Abstract

In Germany, the severity of a narcotic offence is determined based on the classification into different categories of quantity. Recently, an amendment to the Narcotics Law regarding the "not inconsiderable quantities" was introduced. The new limits for methamphetamine are derived from the varying potency of the respective enantiomers. Switzerland, however, does not practice this distinction and there is only one limit quantity, without considering the isomeric structure. To examine whether this single value is still contemporary, 26 Thai pill samples from the years 2000, 2001, 2007, 2009 and 2017 were analyzed by HPLC-MS/MS and GC-MS. Both methods resulted in similar stereoisomeric distributions: the pills mainly consist of the more potent S-(+)-methamphetamine, some even being enantiopure. Others show enantiomeric mixtures of R-(-)-/S-(+)-methamphetamine, but rarely in an equimolar ratio. There even was one sample, where mainly the less potent R-(-)-methamphetamine was detected. In conclusion, the analyses revealed that the single value for a "not inconsiderable quantity" in Switzerland seems outdated. Most of the sized pills showed a much higher concentration of the more potent S-(+)-methamphetamine. The risks related to taking such a pill are much higher and therefore the limit quantity should be adapted to the potency of the respective enantiomers.