Postmortem blood free and total morphine concentrations in medical examiner cases

This purpose of this study was to determine the relationships between postm ortem free morphine and total morphine levels in a large series of medical examiner morphine and heroin related deaths. Free morphine, total morphine, and 6-monoacetylmorphine (6-MAM) concentrations were measured by gas chrom atography-mass spectrometry (GC-MS) in 87 medical examiner cases over 20 mo nths. The mean total morphine concentration, mean free morphine concentrati on, and mean percent free morphine for all cases were: 2.3 mg/L (SD 5.2 mg/ L), 0.5 mg/L (SD 1.6 mg/L), and 19.4% (SD 22.8%); respectively. Regression analyses showed weak correlations between total and free morphine concentra tions over the entire concentration range (0 to 36.6 mg/L, r = 0.603, n = 9 1) and over a subset concentration range of 0 to 1.0 mg/L (r = 0.369, n = 5 4). Twenty-three out of 56 (41%) tested positive for 6-MAM, indicative hero in abuse cases. Lower total and free morphine concentrations and a higher p ercent free morphine were found in individuals with detectable 6-MAM. Compa ring blood concentrations for cases with and without detectable 6-MAM demon strated mean total morphine concentrations of 0.9 mg/L versus 2.1 mg/L (p = 0.05), mean free morphine concentrations of 0.3 mg/L versus 0.4 mg/L (p = 0.21), and mean percent free morphine of 34.7% versus 13.7% (p < 0.003), re spectively. Our findings demonstrate higher free to total morphine ratios i n individuals with detectable 6-MAM than in individuals without 6-MAM. The database established in this study may assist medical examiners in the eval uation of postmortem blood opiates regarding the cause of death in opiate r elated ingestion cases.