Time course detection of dihydrocodeine in body hair after a single dose

Abstract

When head hair is not suitable or not available, body hair, such as leg or beard hair might be the most suitable sample for drug hair analysis. Drugs may be detected in beard, from the first day up to more than one week. Specific information about the time course detection of drugs, after a single intake, in body hair has not been yet well documented for the different body hair samples. The aim of this study was to determine and compare the detection window of dihydrocodeine in frequently shaved legs and beard after a single intake. Unshaved hair from head hair, chest hair, leg hair, and/or arm hair were also analysed. Before a single intake of 12 mg dihydrocodeine by test subject 1 (female), the leg hair was shaved in the morning. The second test subject 2 (male) shaved his beard in the morning and 30 min later he had a dose of 10 mg of dihydrocodeine. The samples were washed with water and shampoo, dried and collected as follows: subject 1: every 3-days shaved leg hair ( n = 10) and 1-month-later head hair ( n = 1). Subject 2: daily shaved beard hair ( n = 15), 2 months later head hair ( n = 50, different regions), and every 20 days unshaved arm, leg and chest hair (from different regions) ( n = 4/area). The samples were analysed for dihydrocodeine using a validated liquid chromatography tandem mass spectrometry method with a limit of quantification (LOQ) of 16 pg/mg for dihydrocodeine. About 20 mg of hair samples were weighted, washed with dichloromethane, centrifuged, dried, and pulverized in the same disposable tubes. Then the samples were incubated with methanol (under sonication at 45 °C) during 4 h. After centrifugation, the supernatant was evaporated and a cation exchange solid phase extraction followed by separation and quantification using ultra performance liquid chromatography tandem mass spectrometry (UHLC-MS/MS) was carried out. Chromatographic separation was achieved using a BEH phenyl column eluted with 0.1% formic acid: methanol (0.1% formic acid). The UPLC-MS/MS method was validated and used in routine for drug hair analysis for already several years [1] . In the present study leg hair was collected every 3 days, as an average of frequent shaved hair in western woman population. Leg hair was very limited and only one hair sample from both woman legs was available per analysis. Beard was collected daily and in a higher amount. Dihydrocodeine was detected in leg hair from the first sample (3 days after the intake). Maximum concentration at 68 pg/mg for the single intake was obtained after 15 days (± 2 days), decreasing later to the LOQ from the 21st day. Beard hair was already positive from the first day sample, and the maximum concentration was observed at 66 pg/mg, 6 days after the intake, decreasing later to the LOQ from day 10. This may be explained by the ‘Richards–Meharg body and head hair growth table, where it indicates that legs have only 20% of growing hairs in anagen phase, while beard goes from 50 to 70%. In other body hair samples, dihydrocodeine was negative or detected from 1 month after the intake. Body hair presents different time course window detection due to the different growth rates. Frequently shaved leg and beard hair may be suitable samples for recent single dihydrocodeine dose detection from the first days up to 21 or 13 days after the intake, respectively, when an LOQ of 16 pg/mg is applied.