Hair analysis: an alternative sample for toxicological analysis of drugs of abuse

What are drugs of abuse?

A clear definition of what drugs of abuse are may be the one proposed by Cabrera and Torrecilla in their Manual on Drug Dependence (1988), where they indicate that they are “all those substances that produce dependence and that are used voluntarily to provoke certain sensations or psychic states that are not therapeutically justified”.

What are drugs of abuse and how do they affect us?

All substances that alter our psychic functions (whether legal or illegal) can be simply classified into three large groups according to their pharmacological effects:

  1. Depressant drugs: these are substances that decrease or slow down the different functions of the Central Nervous System. The most important substances within this group are:
    • Alcohol
    • Opium derivatives such as heroin, morphine or methadone, among others.
    • Different drugs indicated to calm anxiety (anxiolytics), to help sleep (hypnotics) or that act as muscle relaxants.
  2. Central Nervous System (CNS) stimulant drugs: These are substances that accelerate the normal functioning of the brain and cause a state of high activation. Within this group of drugs are:
    • Major stimulants, such as amphetamines, cocaine or speed.
    • Minor stimulants, such as nicotine in tobacco and xanthines, such as caffeine, theine and theobromine (the latter is found, for example, in cocoa).
  3. Disruptive drugs: These substances seriously alter the functioning of the brain, giving rise to very varied effects depending on the substance in question. Within this group it is worth mentioning:
    • The most typical hallucinogens such as LSD, mescaline or peyote.
    • Cannabis derivatives, such as hashish and marijuana.
    • Synthetic drugs, such as ecstasy or MDMA.

Is there treatment for drugs of abuse?

The first stage of detoxification treatment can be a difficult process, as the patient is likely to have abused several drugs with different pharmacological actions. On many occasions, patients do not remember or deny the simultaneous use of several products, therefore the diagnostic assessment should always include a urinalysis for the qualitative detection of psychoactive substances and their metabolites.

Hospitalization or care in a residence specialized in drug addiction treatment are the ideal means to treat a poly-drug addiction, mainly during the detoxification phase, as well as the initial phase of drug withdrawal, since the ineffectiveness, even the danger, of outpatient detoxification has been proven for patients who have abused several drugs, as indicated by Mello NK and Mendelson JH in their chapter Cocaine and other frequently abused drugs in the book Principles of Internal Medicine (2016).

Disturbances caused by drug abuse usually improve with effective treatment, but relapses can occur unpredictably.

Are there advances in toxicological analysis?

The different biological samples used in toxicological analysis of drugs of abuse have been evolving with great efficiency in recent years. In addition to blood and urine, which have been the most commonly used biological samples for the analysis of these drugs, “alternative samples” have been incorporated, such as hair, which have shown significant advantages, at least in certain aspects, over traditional samples (blood and urine).

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This has been possible thanks to the development of highly sensitive analytical techniques, which allow the use of samples where there is generally a low quantity and concentration of the toxicant. Likewise, the minimum amount of hair sample necessary for the analysis of drugs of abuse should be between 60 and 100 mg of hair, which would be equivalent to a strand of hair, approximately the thickness of a pencil. However, it should be noted, as a drawback of the analysis of drugs in hair, that this type of study cannot establish a correlation between the dose consumed and the concentration detected, since there is great individual variability in the retention of drugs in hair, as indicated by Bermejo and Tabernero in ‘Determination of drugs of abuse in hair’ (2011).

The minimum concentrations above which a result should be considered positive for the different types of drugs identified in hair samples are:

  • Opiates: should be considered positive from 0.2 ng/mg in screening tests and 0.2 ng/mg for each substance in confirmatory tests.
  • Amphetamines: For this drug the cut-off point was established at 0.2 ng/mg in screening techniques and 0.2 ng/mg of each amphetamine in confirmatory techniques.
  • Cocaine: Positive at 0.5 ng/mg for screening techniques and 0.5 ng/mg for cocaine and 0.05 ng/mg for each of its metabolites in confirmatory techniques.
  • Cannabis: The minimum detectable value in the screening analytical methods was 0.1 ng/mg and the same values for THC in the confirmation techniques, while for its metabolite THC-COOH (11-nor-9-carboxy tetrahydrocannabinol), 0.2 pg/mg, is the minimum detectable amount. The identification of the latter is essential to establish cannabis consumption, even at low concentrations.

What are the applications of the analysis of drugs of abuse in hair?

Among the different applications of the analysis of drugs of abuse in hair, one of the most important is the monitoring of patients undergoing drug treatment, since this methodology allows sequential control of therapeutic compliance. In the same way, it is very useful in criminal prosecutions, thus replacing the frequent urine tests. It is also used to demonstrate habitual consumption of drugs of abuse in subjects who have been brought before a court and whose criminal liability may be modified by their drug-dependent status. In the latter case, the forensic doctor will be in charge of taking the sample and will determine the need for the test as a diagnostic means to prove such addiction.

In addition, hair drug testing can be used in civil child custody proceedings to control drug use by either parent or in the workplace to control substance abuse among employees. This type of analysis is also used to detect the administration of depressants (benzodiazepines, ketamine, GHB, etc.) to the elderly for criminal purposes, as well as in cases of sexual assault.