Concentrations of zolpidem and zopiclone in venous blood samples from impaired drivers compared with femoral blood from forensic autopsies.

The concentrations of zolpidem and zopiclone were determined in peripheral blood samples in two forensic materials collected over a 10-year period (2001-2010). The z-hypnotics were determined in venous blood from living subjects (impaired drivers) and in femoral blood from deceased persons (forensic autopsies), with the latter classified as intoxication or other causes of death. The z-hypnotics were determined in blood by capillary column gas chromatography (GC) with a nitrogen-phosphorous (N-P) detector after solvent extraction with n-butyl acetate. The analytical limit of quantitation (LOQ) was 0.02 mg/L for zopiclone and 0.05 mg/L for zolpidem and these have remained unchanged throughout the study. When death was attributed to drug intoxication (N=918), the median concentration of zopiclone in blood was 0.20 mg/L compared with 0.06 mg/L for other causes of death (N=1215) and 0.07 mg/L in traffic offenders (N=691) (p<0.001). Likewise, a higher median concentration (0.30 mg/L) was found in intoxication deaths involving zolpidem (N=357) compared with 0.13 mg/L for other causes of death (N=397) or 0.19 mg/L in impaired drivers (N=837) (p<0.001). Median concentration in blood of both z-hypnotics were appreciably higher in intoxication deaths when no other substances were identified; 0 70 mg/L (N=12) for zopiclone and 1.35 mg/L (N=12) for zolpidem. The median concentrations of z-hypnotics in blood decreased as the number of co-ingested substances increased for intoxication deaths but not other causes of death. The most prevalent co-ingested substances were ethanol in autopsy cases and diazepam in the motorists. This large compilation of forensic cases should prove useful when toxicologists are required to interpret concentrations of z-hypnotics in blood samples in relation to cause of death.