Zeiteinschätzung des Konsums von Stimulantien in Blutserumproben über enantioselektive Analytik
Date issued
Authors
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
License
Abstract
Amphetamine-type stimulants (ATS) are a globally abused type of narcotic drugs. Effects range from stimulant effects such as increased concentration ability and psychomotor performance to restlessness, confusion and aggression. The acute phase is followed by symptoms of exhaustion such as fatigue and lack of concentration, which can last for days. Due to their psychomimetic properties and the widespread use of ATS, forensic toxicologists are frequently confronted with the assessment of offenses related to the consumption of these stimulants. These primarily include questions related to driving ability, but also the assessment of criminal responsibility. In this context, experts are often challenged by the fact that it is hardly possible to make statements regarding the influence at the moment of the crime, in particular due to the unknown quantity consumed. The verification of the defendant's information on the time of the last consumption is therefore of crucial forensic interest. While time estimation based on blood serum concentrations as determined routinely in forensic laboratories is not possible, enantioselective analysis offers an approach that potentially expands the forensic interpretation possibilities. Since ATS are mostly consumed as racemates, but their enantiomers are metabolized at different rates in the human body, conclusions can be drawn about the time of consumption if the time course of the enantiomeric ratios is known. The studies summarized in this dissertation describe the investigation of the enantioselective pharmacokinetics of 4-fluoroamphetamine (4-FA) and amphetamine with respect to forensic issues. In addition, the plasma protein binding (PPB) of various ATSs was determined enantioselectively and seized substance samples of illicit ATS were analyzed for their chiral composition.
For this purpose, two liquid chromatographic-tandem mass spectrometric (LC-MS/MS) methods for the detection of the enantiomers of amphetamine, methamphetamine, 4-FA, 3,4 methylenedioxy-N-methylamphetamine (MDMA), and the amphetamine metabolites norephedrine and 4-hydroxyamphetamine were developed and successfully validated for application in serum samples. Sample preparation was performed by solid phase extraction (SPE) and enantiomer separation was performed using a chiral column.
The analysis of police seizures showed exclusively racemic composition for amphetamine and MDMA. On the one hand, this allows the interpretation of enantiomeric ratios in serum for the purpose of time estimation and, on the other hand, the differentiation from a therapeutic intake of approved (S)-amphetamine-containing drugs. While the majority of the seized methamphetamine samples exclusively contained the more potent (S)-enantiomer, in some cases the pure (R) enantiomer as well as racemic and non-racemic mixtures were also detected. These results reflect the current changes in the drug market and may also have legal implications for the interpretation of the so-called ‘nicht geringe Menge’ (non-small amount) according to the German Narcotics Act (BtMG).
Analysis of serum samples obtained from 12 subjects in a clinical study with oral ingestion of 4 FA showed significantly shorter half-lives for the (S)-enantiomer. The increase in (R)/(S) concentration ratios was linear for all subjects and was independent of the given dose. However, the slope of the (R)/(S) ratios showed considerable interindividual differences, resulting in enantiomeric ratios between 1.08 and 2.77 after 12 hours. Nevertheless, for forensic interpretation, a cut-off at a (R)/(S)-ratio of 1.60 could be suggested, indicating the absence of acute effects.
For time estimation in amphetamine use, samples were collected from psychiatric inpatients who voluntarily provided information on their last consumption. Here, a good correlation of the (R)/(S) concentration ratios with the reported time difference to the last consumption was found, although significant outliers were also observed. Analogous to the 4-FA study, this study indicated a cut-off at a (R)/(S) ratio of 1.09 for the assumption that acute effects have passed. Limitations include the relatively small sample size of 30 samples, the reliability of the self-reported data and the frequent presence of binge consumption. Examination of a total of 425 amphetamine-positive forensic serum samples yielded (R)/(S) concentration ratios between 0.88 and 4.04. Furthermore, the enantiomers of the metabolites norephedrine and 4-hydroxyamphetamine could be detected in many of these samples.
The determination of the PPB of amphetamine, methamphetamine, 4-FA and MDMA by ultrafiltration (UF) revealed no or only insignificant differences in the binding of the enantiomers. A significant influence of the PPB on the stereospecific differences in pharmacokinetics and pharmacodynamics could therefore be excluded.