Further evidence for the presence of GHB in postmortem biological fluid: implications for the interpretation of findings

Analysis and interpretation of the findings for the drug of abuse gamma hydroxybutyric acid (GHB) in fatalities has become very problematic. This is primarily because of variable data in postmortem biological fluids resulting from the endogenous nature of the compound, possible postmortem production, and varying methods of detection. Preliminary studies support the use of plasma standards in determining urinary GHB concentrations and indicate measurement of GHB in postmortem biological fluids may be dependent on the method of analysis. In order to assist interpretation of postmortem data based on gas chromatography-mass spectrometry (GC-MS) analysis using GHB-d6 internal standard, the results of GHB concentrations measured routinely in postmortem blood and urine specimens in 40 fatalities received during a three-month period are shown. In all cases, GHB was not implicated in the cause of death; there was no apparent correlation between manner of death and resultant GHB concentrations. Mean concentrations of GHB determined in postmortem blood were found to be 12.3 mg/L (range = 2-29 mg/L, n = 38) and 12.6 mg/L (range = 4-25 mg/L, n = 17) (unpreserved and sodium fluoride-preserved samples, respectively) and 5.5 mg/L in unpreserved urine (range 0-18 mg/L, n = 39) and 4.8 mg/L in sodium fluoride-preserved (range 0-10 mg/L, n = 15) urine samples. Vitreous humor was available in two of the cases analyzed (GHB = 1 and 3 mg/L). The data support the potential use of sodium fluoride-preserved samples for interpretation of GHB concentrations, particularly if there has been an extended postmortem interval. In addition, interpretative cut-offs can be proposed for both postmortem blood and urine, based on the specific GC-MS method used. At blood concentrations less than 30 mg/L and at urine concentrations less than 20 mg/L, it is possible that any GHB detected could represent only endogenous GHB production.