Pharmacokinetic study of midazolam and α-hydroxymidazolam in guinea pig blood and hair roots after a single dose of midazolam

Two DFSA cases involving midazolam clarified by the micro-segmental hair analyses

PURPOSE

In this study, an analytical procedure to identify trace amounts of drug in hair based on micro-segmental hair analysis was presented. The method also can be used to estimate the time of drug ingestion at daily precision by cutting a single hair into sub-millimeter segments which correspond to daily hair growth.

METHODS

A method was established for efficient extraction of midazolam, one of the most frequently detected compound in drug-facilitated sexual assault (DFSA) cases, from each 0.4-mm hair segment and validated by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Moreover, two DFSA cases were used to compare the micro-segmental hair analysis with the 1- cm segmental analysis method.

RESULTS

The validation showed a lower limit of quantification of 0.5 pg/mm for midazolam, with intraday and interday accuracies (bias) from  - 5.2 to 0.9%. The micro-segmental hair analysis method was applied to proximal 1-cm hair segment including hair bulbs in two DFSA cases. The micro-segmental hair analysis results in case 1 showed midazolam in the S15-S17 (5.6-6.8 mm from hair bulb) in a concentration range from 0.5 to 0.9 pg/mm, and the concentrations of midazolam in all hair micro-segments (0-1 cm from the scalp) in case 2 were from 0.5 to 2.0 pg/mm.

CONCLUSIONS

Comparison with the conventional method revealed that micro-segmental hair analysis may enhance the utility of hair drug testing and strengthen probative force in DFSA cases.

Current status of hair analysis in forensic toxicology in China

Hair analysis has been mainly used to document drug use history in abusers, drug-facilitated crime cases, doping control analysis and postmortem toxicology in the fields of forensic toxicology, clinical toxicology, and doping control. Hair analysis has also gained more attention in the last 30 years in China. Relevant technology has been promoted as more research has appeared concerning hair analysis, and consensus has been sought among forensic toxicologists regarding aspects such as hair decontamination treatment, detection of abused substances in hair, segmental hair analysis and interpretation of analytical results. However, there are still some limitations in the estimation of drug intake time and frequency by segmental hair analysis due to the different growth cycles evident within a bundle of hairs, the drug incorporation mechanism and sampling errors. Microsampling and imaging mass spectrometry (IMS) technology based on a single hair may be a good choice to estimate drug intake time more accurately. Analysis of hair root samples may also be used to document acute poisoning in postmortem toxicology, and the analysis of the hair shaft can document long-term use of drugs depending on the length of the hair being evaluated.