Postmortem memantine concentration in a non-intoxication case, and the possibility of postmortem redistribution: A case report.

In this case study, we measured the concentration of memantine in the heart blood, peripheral blood, urine, liver, thigh muscle, and subcutaneous fat of a 64-year-old woman who was prescribed memantine for early-onset Alzheimer's disease. She died in hospital after an altercation with her husband. Cause of death was clearly not drug intoxication or overdose, so we investigated the postmortem redistribution (PMR) of memantine in the various tissues and blood ratios of the postmortem samples. Memantine concentrations detected were 1.31 μg/mL in the peripheral blood, 3.95 μg/mL in central blood, 2.09 μg/mL in the urine, 25.54 μg/g in the liver, 1.16 μg/g in the thigh muscle and 2.13 μg/g in the subcutaneous fat. In all samples, the concentrations were higher than the accepted therapeutic range (which is approximately 0.09-0.15 μg/mL). The central blood to peripheral blood (C/P) memantine ratio was 3.01 while the liver to peripheral blood (L/P) ratio was 19.5. It is documented that a C/P ratio exceeding 2 and L/P ratio exceeding 20 highlight a propensity for significant PMR. Although this is a single case study, our data suggest that memantine exhibits PMR. Additionally, a lowered pH was found in peripheral blood (pH 6.2) and central blood (pH 6.1). This postmortem reduction in blood pH may also promote the PMR of memantine. Because there is very little available postmortem toxicological data on memantine, our case study will serve as a foundation to assist in future forensic investigations.