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Investigating Cocaine Use in Hair Samples

Written by: Alan Baker 25th October, 2024

Introduction

When testing for cocaine (COC) in hair samples, one key challenge is distinguishing between ingestion and external contamination. The body can absorb cocaine into the hair both through the bloodstream after consumption and from environmental exposure. Testing for metabolites (the substances formed when the body breaks down cocaine) plays a crucial role in proving ingestion. However, these metabolites can also be present in street cocaine samples as by-products of degradation, complicating the process.

This blog post explores a recent study that examined minor hydroxycocaine (OH-COC) metabolites in seized cocaine and hair samples. It analyses the significance of these metabolites in distinguishing between actual drug use and contamination.

The Study

The research examined 200 seized street cocaine samples and 2389 hair samples collected during routine case work. The study focused on specific minor metabolites, p- and m-hydroxycocaine (OH-COC), along with p- and m-hydroxybenzoylecgonine (OH-BE), which were present in both cocaine samples and hair samples.

Analysts interpreted the hair samples using a well-established decision model that relies on the ratio of metabolites to cocaine. This helps differentiate between drug use and external contamination. The analysis also considered factors such as the case background, hair colour, sample collection site, the sex of the donor, and the metabolic ratios of key metabolites like benzoylecgonine (BE), norcocaine (NC), and cocaethylene (CE).

Key Findings

  1. Street Cocaine Composition: All 200 seized cocaine samples contained p- and m-OH-COC, with a maximum concentration of 0.025% and 0.052%, respectively. p- and m-OH-BE were found in over half of the samples, with maximum levels of 0.044% and 0.024%, respectively.
  2. Hair Sample Analysis: Researcher determined that 424/2389 hair samples (17.7%) were predominantly contaminated. Most of these contamination cases (83.7%) linked to traffic medicine cases likely experienced higher environmental exposure.
  3. Metabolic Ratios: The study found that metabolic ratios of OH-COC metabolites were significantly higher in hair samples from individuals who had ingested cocaine compared to those contaminated through external contact. Forensic cases showed notably higher ratios compared to abstinence controls. Additionally, researchers found higher OH-COC metabolic ratios in black hair compared to blonde or grey hair, though this trend did not appear for OH-BE ratios.
  4. Other Factors: There was no significant difference in the metabolic ratios based on the donor’s sex. However, the OH-COC ratios increased as the ratios of norcocaine (NC) and cocaethylene (CE) to cocaine rose, further suggesting that these metabolites are reliable indicators of cocaine use.

Conclusion

This study highlights the importance of using OH-COC metabolites, along with specific metabolic ratios, in determining whether positive cocaine results in hair samples are due to actual drug use or contamination. Incorporating these minor metabolites into forensic analysis enables professionals to make more accurate interpretations. This approach proves particularly beneficial in challenging cases where analysts suspect contamination.

The findings also reinforce the complexity of analysing hair samples for drug use, as factors, including hair colour, can affect the metabolic ratios. This research supports the need for comprehensive testing methods to ensure reliable results in legal and medical investigations.

Implications for Drug Testing

As hair analysis becomes an increasingly common method for detecting drug use, this provides valuable insights into improving the accuracy of results. Focusing on minor metabolites and metabolic ratios helps forensic and medical experts more accurately distinguish between ingestion and contamination. This approach prevents individuals from being wrongly accused of drug use due to environmental exposure.

 

 

 

 

 

https://academic.oup.com/jat/advance-article/doi/10.1093/jat/bkae064/7738994?searchresult=1&utm_source=Forensic+Library&utm_campaign=c093ae96e7-EMAIL_CAMPAIGN_2024_09_17_12_02&utm_medium=email&utm_term=0_-c093ae96e7-%5BLIST_EMAIL_ID%5D&mc_cid=c093ae96e7&mc_eid=96c196b96d