Cocaine Hydroxy Metabolites in Hair: Indicators for Cocaine Use Versus External Contamination☆.

Given that external contamination must be considered in hair analysis, there is still a demand for reliable tools to differentiate between incorporation of drugs into the hair as a result of drug consumption and of the hair shaft by external contamination. With the aim of establishing alternative discrimination parameters, some of the hydroxy metabolites of cocaine i.e., para- and meta-hydroxycocaine and para- and meta-hydroxybenzoylecgonine were measured together with cocaine, benzoylecgonine, cocaethylene, and norcocaine in five seized street cocaine samples and in hair samples from different cohorts: cohort 1 (in vivo external contamination study, n = 28), cohort 2 (individuals with self-reported cocaine use, n = 92), and cohort 3 (individuals with suspected cocaine use or contamination, n = 198). Statistical evaluation of the data of cohort 1 and 2 using ROC curves yielded metabolic ratios indicating cocaine use. Based on these results, a decision workflow was established for the discrimination between cocaine use and external contamination. The power of this approach was finally statistically validated across the different cohorts.