Hair Strand Drug Testing and How Metabolites Aid Detection

Hair strand drug testing is now commonly used by local authorities, employers, in court cases, and in sports to detect for the misuse of drug substances. In this test, a sample of the hair is taken to be analyzed for traces of the drug and its metabolites.

Why is hair strand testing effective?

When a drug is consumed by the body, it is incorporated into the bloodstream. The bloodstream directly feeds the growth of the hair, meaning that traces of the substances it contains are transferred to the hair follicle and eventually into the hair shaft. Therefore, when the hair grows, evidence of any drug consumption grows with it.

As the rate of hair growth is on average 1 cm per month, a 3-cm sample of hair can provide evidence for three months of past drug use. However, hair strand testing is not effective until at least two weeks following consumption, since this is the time required for the hair to grow a sufficient length for analysis.

How do metabolites aid in hair strand testing?

Metabolism refers to the chemical reactions that take place within the body to break down and use molecules that are ingested for use as energy or other materials. The process usually takes place in the liver, where enzymes stimulate what are referred to as catabolic changes. Just like food, drugs are broken down into smaller, simpler molecules, allowing them to “activate” or take effect and then be used by the body.

All the molecules involved in metabolism are called metabolites. The end metabolites that result from the chemical reactions are then either used in other areas of the body or removed. Because these metabolites are also incorporated into the bloodstream, they too are transferred into the hair follicle, along with the trace of the drug.

This means that when scientists undertake hair strand testing they not only analyze for traces of the drug, but for traces of its metabolites. And, since these metabolites can only be produced from ingestion, their presence is clear evidence that the drug has been consumed, ruling out the possibility that traces of the drug reached the hair shafts externally.

Because specific metabolites are produced per drug, the detection of these substances also provides evidence of exactly which drug has been consumed.

What is the hair strand testing process?
Hair strand drug testing can be undertaken in one of two ways:

1. The segmentation method

Hair strand testing experts use the segmentation method to determine a representation of drug use on a month-by-month basis. This method is helpful for discovering trends, periods of increased or decreased use, or isolated instances. In this process, the sample of the hair is cut into 1-cm samples to each represent the period of a month. Thus, if a hair strand test was required to show results for a three-month period, scientists could uncover three individual results from a 3-cm sample of hair.

2. The overview method

The overview hair strand testing method is used to detect one result for drug consumption over a three-month period. This means if a drug test was required for a six-month retrospective profile of consumption, the investigation would uncover two results—one to represent each three-month period. This less detailed test is effective when only evidence of the presence or absence of the drug is required.

Which drugs can be discovered by hair strand testing?

Hair strand testing can effectively discover the presence of most common illegal drugs:

  • Antidepressants
  • Benzodiazepines
  • Codeine
  • Amphetamines
  • Morphine
  • Rohypnol
  • Buprenorphine
  • Cannabis
  • Heroin
  • Cathinone
  • Cocaine
  • Hypnotics
  • Dihydrocodeine
  • Ketamine
  • LSD
  • Opiates
  • Tramadol
  • Mephedrone
  • Methadone
  • Methamphetamines
  • Ecstasy
  • PCP

Hannah Richards writes on behalf of Lextox, a leading U.K. drug testing laboratory;

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