Relationship Between Postmortem Urine and Blood Concentrations of GHB Furnishes Useful Information to Help Interpret Drug Intoxication Deaths.

This article reports the concentrations of gamma-hydroxybutyrate (GHB) in femoral blood and bladder urine in a case series of drug intoxication deaths (N = 37). GHB was determined in blood (B-GHB) and urine (U-GHB) by a GC-FID-GBL method and 30 mg/L was used as a cut-off concentration for reporting positive results. The mean (median) and range of GHB concentrations in bladder urine were 2,818 mg/L (1,900 mg/L) and 120-13,000 mg/L, respectively. These concentrations were appreciably higher than those in femoral blood, 637 mg/L (260 mg/L) and 30-9,200 mg/L, respectively. Urine/blood ratios of GHB were highly variable (mean 8.99, median 5.33 and range 0.16-29.3). GHB is rapidly metabolized and cleared from the bloodstream, whereas there is no metabolism occurring in the urinary bladder. In five autopsy cases, U-GHB was lower than B-GHB, which suggests that these individuals died before equilibration of the drug in all body fluids and tissues. In the other 32 deaths, U-GHB was higher than B-GHB, sometimes appreciably higher, which points towards a longer survival time after intake or administration of GHB. The analysis of urine extends the window of detection of GHB by several hours compared with blood samples, depending in part on when the bladder was last voided before death. Furthermore, the urinary concentration of GHB gives a hint about the concentration in blood during the time that the urine was produced in the kidney and stored in the bladder since the previous void.