A study of free and total morphine in heroin death of chronic users

Heroin is a widely abused substance, involved in a large number of deaths. It has been seen that long-term exposure to street heroin results in an increase in morphine glu- curonide metabolites. This suggested us that there might be a relationship between blood morphine metabolites concentrations and heroin-related deaths. In particular, the concen- tration of morphine glucuronide metabolites could be higher in delayed heroin-related death compared to rapid heroin-related deaths. To evaluate this hypothesis, 53 forensic autopsies of heroin-related death collected between 2016 and 2022 were divided into two groups: chronic user (CU) and non-chronic users (NCU), on the basis of the morphine positivity in hair. The dif- ference of blood free morphine concentrations (FM), blood total morphine concentrations (TM) in blood and bile morphine concentrations (BTM), in the two groups were statistically analysed. Also, the FM/TM ratios were calculated. FM was used to analyse the difference of immediate, subacute and delayed deaths in the two groups. The results showed that the median FM value in the CU group was non-statistically higher than in NCU one. The CU group showed a significantly higher median TM and BTM values, but a significantly lower FM/TM value than in NCU group. Furthermore, the CU group showed a significantly higher percentage of FM in delayed deaths than NCU group. In conclusion, measurements of blood variables indicate a shift in morphine metabolites that could be involved in heroin-related death among chronic users, possibly being a risk factor for delayed causes of death of drug users.