Incorporation of Isotopically Labeled Cocaine into Human Hair: Race as a Factor

In order to evaluate race as a possible factor affecting the incorporation of drugs into human hair, 2 mg/kg deuterium-labeled cocaine (cocaine-d5) was administered intranasally to nine male non-Caucasian volunteers under controlled laboratory conditions. Sequential blood samples were collected for up to three days, and scalp hair samples were collected at 24 and 72 h after dosing and at monthly intervals for up to 12 months. The samples were then analyzed by gas chromatography-mass spectrometry for cocaine-d5 and benzoylegonine-d5 (BZE-d5). The amounts of cocaine-d5 found in the hair of these non-Caucasian subjects were compared with the amounts of cocaine-d5 found in the hair of Caucasian subjects who received the same cocaine dose under identical conditions as part of a study we reported previously. The non-Caucasians in the present study had approximately 2.7 times more cocaine-d5 in their hair than the Caucasian subjects in the earlier study. In five of the non-Caucasian subjects, cocaine-d5 could be detected in hair within 24 h after dosing. Curiously, we were unable to detect any cocaine-d5 in one of the non-Caucasian subject's hair at any time after dosing even though cocaine-d5 was in plasma at the expected levels. The results from these studies suggest there may be a racial bias in the incorporation of cocaine into human hair; however, the data are not conclusive because of the relatively small sample size.