Drugs in hair. Part I. Metabolisms of major drug classes.

Currently, hair can be reliably tested for the presence of drugs. However, one major drawback to the use of parent drugs is the question of potential external or environmental contamination. The analysis of metabolites to confirm the use of the parent drugs was proposed in this short review. The development of hair as a test matrix and the incorporation of xenobiotics, in general, into the hair matrix were discussed. What constitutes an appropriate metabolite for drug testing to mirror the use of a parent drug was proposed and discussed. The use of metabolites rather than parent drugs to indicate unequivocal use rather than external exposure was also discussed for amphetamines, cannabinoids, cocaine, opiates (codeine, morphine, 6-acetylmorphine, hydrocodone, hydromorphone, oxycodone, oxymorphone), phencyclidine, fentanyl, benzodiazepines, and ethanol. This, however, was discussed in terms of class and/or individual drug. In addition, selection or potential selection of appropriate metabolites was reviewed. The actual incorporation of drug metabolites into hair versus the metabolism of drugs which was incorporated into hair were also considered.