Cocaine and benzoylecgonine concentrations in fluorinated plasma samples of drivers under suspicion of driving under influence

Abstract

Due to an in vitro decomposition of cocaine (COC), usually an analytical detection in unstabilized blood taking systems is impossible and for this reason the main metabolite benzoylecgonine (BZE) is determined. In a few regions in Germany the local authorities use systems containing sodium fluoride for taking a blood sample. Caused by inhibition of esterases in the taken sample COC is still detectable in blood samples. Cases of driving under the influence (DUI) with positive findings for COC and/or BZE were evaluated and substance concentrations in plasma were correlated with documented deficiencies in the psycho-physical performance. In 51.5% of all cases positive for cocaine-like substances besides BZE a positive result was also given for COC. If both substances were found (mean COC concentration 0.836 mg/L) the concentration of BZE was significantly higher (mean 0.669 mg/L) compared to cases with a single detection of BE (mean 0.209 mg/L) (p=0.001). In 72 cases without any detection of further drugs cocaine users seemed rather excited and stimulated towards intervening police officers, in particular when COC was present in the blood (17.8%). Also in the medical investigation reports a rather stimulative effect (25% vs. 3.6% sedated) was to be registered. Whereas with a sole determination of BZE, a stimulated (19%) as well as a sedated impression (14.9%) was described. Definite concentration-effect relations could not be recognized. Indeed, more peculiarities were to be registered with the simultaneous detection of COC than with a sole BZE determination. The determination of COC and the differences in the BZE concentration can be explained by the fact that the simultaneous detection of both substances is indicative for of a consumption shortly before the blood sampling. A sole detection of BZE is more likely indicative for a consumption already some time ago. Therefore, in the first case one would rather suggest an acute intoxication phase. A determination of BZE without COC is more likely indicative for a transition to the drug-induced exhaustion phase which is also to be expected after the consumption of COC. The absence of COC can be seen within the scope of a validity check as an indication of a possible exhaustion reaction. A use of fluoride stabilized blood sampling systems is advised. This makes it easier to investigate the state of intoxication or to appraise the temporal connection between COC consumption and incident or blood sampling.