Effect of pigmentation on the drug deposition in hair of grey-haired subjects.

The hair samples of 15 grizzled patients with a permanent medical treatment by amitriptyline, carbamazepine, chlorprothixene, diclofenac, doxepine, indomethacine, maprotiline or metoclopramide, or with a chronic heroin and cocaine abuse were separated into white and pigmented fibers and both fractions were independently investigated by GC-MS. The drugs were found in pigmented fibers as well as in white fibers, but the concentrations in the white fibers were smaller than in the pigmented ones for the most of the samples investigated. The concentration ratio of the drugs or their metabolites in both hair fractions (white/pigmented) was found to be between 0.09 and 1.57 (mean 0.70, 30 concentration pairs). There are large differences in this ratio between different subjects with the same drug, whereas for different drugs in the same subject in many cases similar ratios were measured. As a reason a different grade of pigmentation of the hair and the influence of the drug structure are discussed. From these results it follows that the natural hair colour is an important parameter in the evaluation of drug concentration in hair.