A reduction in blood morphine concentrations amongst heroin overdose fatalities associated with a sustained reduction in street heroin purity.

To determine the effects of a sudden and sustained reduction in heroin purity on the toxicology of heroin overdose, 959 consecutive heroin overdose cases autopsied at the NSW Department of Forensic Medicine (1/1/1998-31/12/2006) were analysed. There was a significant reduction in blood morphine concentration across the study period (beta=-0.07), declining from a median of 0.50mg/L in the years 1998-2000 prior to 0.40mg/L in the period 2001-2006. There was no significant change in the proportion of alcohol positive cases, but the proportion of benzodiazepine positive cases increased across time (OR 1.11), as did methadone positive cases (OR 1.12). The decline in blood morphine concentrations remained significant after controlling for these factors (beta=-0.07). In determining toxic and lethal morphine concentrations, the fact that the toxicology of overdose is responsive to changes in the opioid street market needs to be borne in mind.