Hairy time for heroin

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  • Published: Jan 5, 2009
  • Author: Steve Down
  • Channels: Gas Chromatography
thumbnail image: Hairy time for heroin

It has been almost two decades since the analysis of illegal drugs in hair began to become a reality and it started to be offered as an alternative mechanism for confirming drug use. In the UK, forensic hair analysis is now offered regularly and the resulting data are used by coroners to help them in their deliberations. Although interpretation of the data is still not as clear-cut as that of drugs in urine or blood, it can offer an insight into the history of drug use in an individual.

Drugs such as heroin accumulate in hair on the head but do not appear to migrate along a hair strand. So, as the hair grows, the amounts of a drug incorporated into the hair segments change with the amount in a user's system. Knowing the growth rate of the hair, it is possible to see when a recent user first began to take drugs and how that changed over time. This method offers a much longer period for detection than biological fluids, up to several months if the hair is allowed to grow long.

If drug addicts attempt to avoid the test by shaving their head, hair from other parts of the body can be substituted. Facial hair, pubic hair and arm and leg hair all accrue drugs, so can confirm drug use, but their slower growth rates make it more difficult to map consumption over time.

In the case of heroin, the parent drug is not the main target in hair analyses. Heroin is metabolised to 6-acetylmorphine (AM) and morphine, as well as the morphine glucuronides and other metabolites. AM and morphine are commonly measured in biological samples to confirm heroin use and one study published by Fritz Pragst and colleagues in 2005 proposed using the results from hair analyses to define ranges by which drug consumption could be classified as low, medium or high. They were determined statistically from a set of illegal heroin users using the minimal value to the 25th percentile (low), 25-75th percentile (medium) and 75th percentile to maximum (high).

A team of scientists from Imperial College London decided to check these ranges using a set of postmortem hair samples from deaths occurring over 2004-2007. They also extended the sampling to pubic hair. Sue Paterson, Sooyeun Lee and Rosa Cordero examined 82 head hair samples cut into a total of 173 segments of various lengths as well as 15 pubic hair samples which were kept intact.

All samples were analysed by an established GC/MS method. After washing and cutting, they were hydrolysed overnight with dilute acid, before mixed-mode SPE. The extracts were subjected to a two-step derivatisation to form the acetylated and trimethylsilylated derivatives for analysis in selected ion monitoring mode.

The lower, medium and upper use ranges in head hair were 0.1-0.9, 0.9-12.5 and 12.5-154.1 ng/mg for AM and 0.1-0.8, 0.8-6.0 and 6.0-36.3 ng/mg for morphine. These values were very similar to those reported in the earlier study, even though protocols were different. Different populations of drug users were tested, one set was alive and one was dead, and the experimental methods were not the same.

The similarity prompted Paterson and colleagues to declare that the values can be used as reference ranges to indicate the relative amounts of heroin consumed. The low range corresponds to low or occasional use (once or twice a week), the middle range to regular use (daily) and the upper range to heavy, excessive use.

The values for pubic hair were lower than head hair at 0.2-0.5, 0.5-2.3 and 2.3-18.2 ng/mg for AM and 0.2-0.4, 0.4-2.4 and 2.4-13.3 ng/mg for morphine. The team would like to see more data to confirm this deviation.

In a second aspect of their study, the UK group wanted to test a recommendation of the Society of Hair Testing (SOHT) that the morphine-AM concentration ratio can be used to prove heroin ingestion, with values less than 0.77 being positive. Problems might arise because illicit heroin is often contaminated with acetylcodeine, which is metabolised to codeine, then morphine, in the body. In addition, heroin addicts often take codeine with their heroin.

The morphine-AM ratios measured by Paterson varied from 0.14 to 17.00, with mean and median values of 1.93 and 0.44, respectively. Clearly, there is a large spread and the results do not support the SOHT recommendation.

The ratio decreased as the concentration of AM increased, suggestive of a modified metabolism in heavy drug users, say the researchers. The ratio also decreased with distance along the hair away from the head, which might be due to exposure of the older sections to drug transfer from sweat or sebum.

Apart from confirming the reference ranges for the level of drug use, the overriding conclusion is that drug analysis in hair is affected by several factors which can influence the results and great care should be taken during their interpretation.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.


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