Enantiomeric profile of amphetamines in seized drug samples and in blood of impaired drivers in Iceland: The rise of (R)-methamphetamine?

Amphetamine (AMP) and methamphetamine (METH) use is increasing globally. Illegal AMP is generally a racemic mixture, whereas AMP-containing attention-deficit hyperactivity disorder drugs prescribed in Iceland consist of S-AMP. AMP is also a main metabolite of interest after METH intake. Distinguishing between legal and illegal AMP intake is vital in forensic toxicology. A chiral UPLC-MS-MS method was used to determine the enantiomeric profile of AMP and METH in circulation in Iceland by analysing blood samples from drivers suspected of driving under the influence of drugs (DUID) and seized drug samples from 2021 and 2022. All seized AMP samples (n = 48) were racemic, whereas all but one seized METH sample (n = 26) were enantiopure. Surprisingly, a large portion of the enantiopure METH samples was R-METH. DUID blood samples positive for AMP (n = 564) had a median blood concentration of 180 ng/mL (range 20-2770 ng/mL) and a median enantiomeric fraction (EFR) of 0.54 (range 0-0.73), whereas samples positive for METH (n = 236) had a median blood concentration of 185 ng/mL (range 20-2300 ng/mL) and a median EFR of 0.23 (range 0-1). The findings of this study show a significantly lower blood concentration in drivers with only S-AMP detected compared with when the R-isomer is also detected. No significant difference in blood concentration was detected between the sample groups containing S-METH, R-METH or both enantiomers. The occurrence of R-METH in both seized drug samples and DUID cases indicates a change in drug supply and a need for better scientific knowledge on R-METH abuse.