Be aware of (R)‐methamphetamine: Negative immunoassay versus positive confirmation analysis

Abstract

The amphetamine‐type stimulant methamphetamine exists in two enantiomeric forms, (S)‐methamphetamine and (R)‐methamphetamine, which are both psychoactive but with the (S)‐enantiomer being more potent than the (R)‐enantiomer. Illicit methamphetamine encountered in Europe is typically a racemic mixture of both enantiomers and enantiopure (S)‐methamphetamine, respectively. However, herein we report two cases with proven enantiopure (R)‐methamphetamine consumption with moreover both cases remaining undetected by immunoassay screening. Inconspicuous immunoassay findings can be traced back to a considerably higher sensitivity and concentration‐dependent cross‐reactivity of the applied drug of abuse assay for the (S)‐enantiomer of methamphetamine compared with the (R)‐enantiomer, and this limitation should be well known by users of immunoassay drug tests.