The use of vitreous humor as an alternative to whole blood for the analysis of benzodiazepines

In postmortem drug analysis, the most commonly used sample matrix is whole blood. However, postmortem changes can denature this matrix, resulting in a loss or degradation of drugs, thus biasing analytical findings. Vitreous humor is thought to be less affected by these changes and should, therefore, have the potential to provide a more reliable estimation of antemortem drug concentrations. To assess the usefulness of vitreous humor for the analysis of benzodiazepine drugs, vitreous humor and whole blood were obtained postmortem in 27 cases. Three benzodiazepine drugs were investigated-temazepam, diazepam, and desmethyldiazepam. For temazepam and diazepam, some correlation was found between the matrices (R2 = 0.789 and 0.724, respectively). However, for desmethyldiazepam, no correlation was observed (R2 = 0.068). Regression analysis on plots of vitreous humor versus blood concentrations produced gradients of less than 1.0 showing that, in general, levels in blood are higher than the corresponding levels in vitreous humor.