The analysis of drugs in hair samples can give a pattern of drug use over a longer period of time, i.e. weeks or months, than other samples, such as urine or saliva, allow. The results can be used to indicate changes in how drugs have been used over a long period of time. The analysis of drugs in hair is a tool that can help when drug use is a problem, but as is the case with the use of any tool, it must be used skilfully.
Interpretation of levels found in hair samples
There are several factors that affect levels of drugs and related substances in hair. For example, the incorporation of drugs into hair varies from person to person, primarily due to physiological differences between individuals.
Other factors affect levels of drug and related substances in hair, in addition to differences in metabolism, examples are: purity and frequency of drug use, physiological aspects such as hair colour, and external factors such as the effect of hair treatments and cosmetics.
These factors can significantly affect the results of a hair test.
Several scientific studies demonstrated a huge inter-individual variation and confirmed the lack of correlation between dose and levels in hair for both therapeutic drugs and illicit drugs(1-8). These studies show that it is not possible to know from the results of one analysis, how much and how often an individual ingested, or how much of a drug an individual took. Nor is it possible to accurately compare data from hair analyses among individuals. On the other hand, the results can be compared with the results previously analysed by the laboratory (9-10). Drug testing is good for showing whether people used drugs or not over a long period of time and it is also possible to use the levels of drugs in hair as a guide to the changes in pattern of use over time in the same individual.
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- Cirimele V, Kintz P, Gosselin O, Ludes B (2000), Clozapine dose concentration relationships in plasma, hair and sweat specimens of schizophrenic patients. Forensic Sci Int 107, 289–300.
- Goullé JP, Noyon J, Layet A, Rapoport NF, Vaschalde Y, Pignier Y, Bouige D, Jouen F (1995), Phenobarbital in hair and drug monitoring. Forensic Sci Int 70, 191–202.
- Jurado, C (2006), Hair Analysis of Cocaine, in Analytical and Practical Aspects of Drug Testing in Hair, (Ed: P. Kintz). CRC Press: London, New York, Washington, 2006, pp. 95–125.
- Pragst F, Rothe M, Hunger J, Thor S (1997), Structural and concentration effects on the deposition of tricyclic antidepressants in human hair. Forensic Sci Int 84, 225–236.
- Takiguchi Y, Ishihara R, Toni M, Kato R, Kamihara S, Uematsu T (2002), Hair analysis of flecainide for assessing the individual drug-taking behavior. Eur J Clin Pharmacol 58, 99–101.
- Tracqui A, Kintz P, Mangin P (1995), Hair analysis: a worthless tool for therapeutic compliance monitoring. Forensic Sci Int 70, 183–189.
- Williams J, Patsalos PN, Mei Z, Schapel G, Wilson JF, Richens A (2001), Relation between dosage of carbamazepine and concentration in hair and plasma samples from a compliant inpatient epileptic population. Ther Drug Monit. Feb;23(1):15-20.
- Pragst F, Broecker S, Hastedt M, Herre S, Andresen-Streichert H, Sachs H, Tsokos M (2013) Methadone and illegal drugs in hair from children with parents in maintenance treatment or suspected for drugabuse in a german community. Ther Drug Monit. Dec;35 (6):737-52.
- Tsanaclis L, Wicks JFC (2007), Patterns in drug use in the United Kingdom as revealed through analysis of hair in a large population sample. Forensic Sci. Int. 2007; 170 (2-3):121-128.