Negative hair test result after long-term drug use. About a case involving morphine and literature review

Abstract

Abstract Although it has been accepted by most scientists that drugs circulating in blood are eligible to hair incorporation, this cannot be considered as a general statement. A 42-year old man was found dead in his swimming pool. He was living alone, and seen alive 2 days before by a neighbour. Femoral blood, cardiac blood and hair were collected during body examination. Free morphine was identified in femoral blood at 28 ng/mL, corresponding to his treatment for chronic pain (3 × 5 mg daily for 4 months). However, with a limit of quantitation (LOQ) at 10 pg/mg, segmental hair testing (3 × 1 cm) for morphine was negative. In this paper, the author has reviewed the different factors which can be responsible of this discrepancy. Several variables can influence the detection of a drug in hair and the author has listed reasons that can account for the absence of analytical response in hair after drug administration. The drug may not be incorporated in hair. That is the case for large bio-molecules, such as hormones, which cannot be transferred from the blood capillaries to growing cells of hair. Cosmetic treatments (perming, colouring, bleaching) or environmental aggressions (ultraviolet radiation, thermal application) will always reduce the concentrations. In this case, the lack of morphine detection was attributed to the effects of chlorinated water from the swimming pool. A negative hair result is also a result. However, this can be interpreted in three different ways: 1. the owner of the hair did not take or was not exposed to the specific drug, 2. the procedure is not sensitive enough to detect the drug, or 3. something happened after drug incorporation (cosmetic treatment, environmental influence).