Blood free morphine levels vary with concomitant alcohol and benzodiazepine use

To record the concentration of morphine in post-mortem blood samples from fatalities arising directly from illicit drug abuse in Grampian, Scotland and to explore whether there is any difference in the morphine levels with co-existent drugs especially alcohol and benzodiazepines.

Drug-related deaths that had positive blood toxicology for morphine from the beginning of January 1995 until the end of December 2001 were identified from the database of toxicological data held in the Department of Clinical Biochemistry, Aberdeen Royal Infirmary, and the data analysed in conjunction with the information in the files of the Forensic Medicine Unit, University of Aberdeen.

One hundred and twenty-six cases were identified and consisted of 106 males and 20 females with an age range 17-51 (Median 26 years). Morphine was the single isolate in only 21 cases giving a median blood free morphine (BFM) of 0.19 mg/L. When morphine and benzodiazepines were the primary isolates [Formula: see text] the median BFM was 0.37 mg/L, and when morphine was in combination with alcohol [Formula: see text] the median BFM was 0.18 mg/L. Statistical significance was noted between these groups ( [Formula: see text] ). The remaining 59 cases had morphine combined with other drugs.

In the studied cases, the concentrations of BFM were statistically higher when morphine was only isolated in conjunction with benzodiazepines than when combined only with alcohol. These results may be multi-factorial; user error while under drug influence, the individuals drug tolerance, or related to the pharmacokinetics of morphine and its interactions with alcohol and benzodiazepines. Our understanding of the interactions of these substances appears to be far from clear.