The stability of diazepam in authentic blood samples from Thai postmortem cases

Abstract

Background: Diazepam is a common drug detected in Thai postmortem cases. The stability of diazepam in blood was previously studied using spiked blood samples. However, there is no available data for stability in authentic postmortem blood samples. Objectives: This study aimd to determine the stability of diazepam in authentic postmortem blood samples. Methods: Postmortem blood samples were obtained from the cadavers of Thai people who were sent for medico-legal autopsies at the Department of Forensic Medicine, Siriraj Hospital, Mahidol University. Blood samples were analyzed for diazepam and nordiazepam within one week after sample reception (initial concentrations: day_0). Subsequently, the blood samples were re-analyzed for diazepam and nordiazepam on the 30th, 60th, 90th, 120th, and 180th days. Descriptive statistics and repeated measures analysis of variance were applied for comparison of the diazepam and/or nordiazepam concentrations over the period of 180 days. Results: There were 24 blood samples recruited for this study. For the statistical analysis, 22 blood samples consisting of diazepam concentrations greater than 10 ng/mL were applied. These 22 samples were classified into low, medium and high concentrations. The mean and median of percent changes from initial diazepam concentrations for low, medium and high groups on the 180th day were-16.8/-12.9,-24.0/-25.9, and-27.9/-22.6, respectively. Diazepam concentrations in the medium and high groups decreased significantly from initial concentrations, particularly on the 120th day and 180th day (P < 0.01). Conclusion: Diazepam concentrations in authentic postmortem blood samples decreased significantly on the 180th day, particularly for medium and high concentrations.