Long-term stability of GHB in post-mortem samples and samples from living persons, stored at −20 °C, using fluoride preservatives

PurposeReanalyses are frequently requested in forensic toxicology, and knowledge of the stability of drugs in biological samples is of major importance for the interpretation of the toxicological findings. Currently, the literature on stability of gammahydroxybutyrate (GHB) in blood samples from living subjects and in post-mortem blood is limited. The purpose of this study was to evaluate the long-term stability of GHB in both blood samples from persons suspected of drug use and post-mortem blood samples.MethodsA total of 59 reanalyses were performed in whole blood samples, 27 samples from living subjects and 32 samples taken at autopsies. The samples were stored in the freezer between 0.4 and 7.2 years at −20 °C in vials containing preservatives. Analyses were performed by GC–FID, and cut-off level was 10.3 mg/L. The concentrations in 22 of the samples were below cut-off.ResultsThe mean change in concentration between initial analysis and reanalysis was −0.8% for the positive samples from living persons and −7.1% for the positive post-mortem samples. Changes ranged from −32.4% to 21.0% for samples from living and from −30.4% to 34.4% for post-mortem samples. All negative samples were still negative at the time of reanalysis.ConclusionReanalysis of these forensic whole blood samples stored several years at −20 °C with fluoride preservation did not exhibit changes in GHB concentrations of practical significance for the interpretation of toxicological findings.