Outside-in hair contamination by blood containing opiates and opioids

Hair analysis for drugs has become extensively used for forensic investigation in recent years. To best interpret hair drug content in post-mortem conditions, the extent of external contamination by biological fluids, such as blood, must be taken into account to avoid false positive results. The present study evaluated opiates and opioids incorporation into hair from blood containing different concentrations of morphine (MOR), 6-mono-acetyl morphine (6-AM), codeine (COD), dihydrocodeine (DHC), tramadol (TRA), oxycodone (OXY), methadone (MET), 2-ethylidene-1,5-dimethyl-3,3- diphenyl pyrrolidine (EDDP), buprenorphine (BUP) and norbuprenorphine (NBUP). The hair strands contaminated by brief soaking into blood were stored at room temperature (RT) or at 4°C during 6 hours, 1, 3, 7 or 14 days. After decontamination by extensive washing, we show that all opiates and opioids were incorporated into hair within a few hours at RT and 4°C, without significant changes over time. The concentrations of opiates and opioids in hair reached the cut-off levels established by the Society of Hair Testing (SoHT) for therapeutic (MET, COD), or toxic or lethal (all other molecules) blood concentrations. The metabolite to parent drug concentration ratios were determined for NBUP/BUP, MOR/6-AM and EDDP/MET and could be helpful as indicators of blood external contamination.