Comparison of blood and urinary ketamine profiles among different causes of death in Thai postmortem cases

Abstract

Background: Ketamine is a commonly abused substance, especially among young adults. Blood and urinary ketamine profiles are important for the interpretation of the cause of death. Objectives: This study aimed to compare the blood and urine ketamine profiles between the different causes of death in Thai postmortem cases and to develop predictive equations for ketamine metabolism in urine. Methods: A cross-sectional study was performed in 40 Thai postmortem cases whose urine samples tested positive for ketamine. Sex, age, cause of death, manner of death, blood alcohol concentration, and concomitant drugs found with ketamine in the subjects were recorded for each case. Blood and urinary ketamine and its two metabolites (norketamine and dehydronorketamine (DHNK)) were analyzed using liquid chromatography quadrupole time-of-flight mass spectrometry. Statistical analysis was performed using the Mann–Whitney U test and Kruskal–Wallis H test. Results: The study subjects included 11 females and 29 males with a mean age of 29.6 years. The causes of death were classified into three groups, namely the road traffic injury (RTI), drug intoxication, and non-RTI groups. The blood ketamine concentration in the non-RTI group was significantly higher than that in the RTI and drug intoxication groups. The two ketamine metabolite concentrations in the urine samples of the non-RTI group were significantly higher than those in the RTI and drug intoxication groups. Male subjects had significantly higher concentrations of blood ketamine and its metabolites than female subjects. Linear regression curves were established between urinary ketamine and norketamine (Log (urinary norketamine) = 1.175(Log (urinary ketamine)) + 0.659; r² = 0.684) and between urinary norketamine and DHNK (Log (urinary DHNK) = 0.045(Log (urinary norketamine)) + 1.147; r² = 0.773). Conclusion: This study developed predictive equations for ketamine metabolism in urine, demonstrating strong correlations between ketamine and its two metabolites. The differences in the ketamine concentrations among the different causes of death and sex potentially indicate drug use patterns rather than direct causal relationships.