Cause of death in heroin users with low blood morphine concentration

The blood morphine concentrations in cases of heroin-associated fatalities can vary considerably. Currently, a free-morphine concentration of > or = 100 ng/ml in blood is generally considered as potentially fatal. Moreover, it is a common observation that fatal cases of heroin-intoxication with blood morphine concentrations lower than 100 ng/ml occur. This poses the question of how the fatal cases with low blood morphine concentrations can be explained. In the study described here, 62 cases of morphine only intoxications were examined. The fatal cases were divided into two groups according to the free morphine concentrations measured in the blood of the heart (group I: free morphine concentration < 100 ng/ml, n = 21 cases; group II: free morphine concentration > or = 100 ng/ml, n = 41 cases). The two groups were compared as to circumstances of death, as well as to autopsy findings and histopathologic alterations. Overall, infections of the respiratory tract occurred significantly more often in group I (lower morphine concentrations) than in group II. In a second step, the group I cases were analyzed individually to get detailed information on the cause of death. In 19 of the 21 cases the authors could find a plausible explanation for death in combination with low free morphine concentrations in the blood.