Distribution of phencyclidine into vitreous humor

Vitreous humor is a fluid contained in the eye that is largely composed of water. The advantages of vitreous humor as a specimen for postmortem drug analysis include its relatively low susceptibility to contamination and the ability to analyze vitreous humor with little or no pretreatment. The postmortem analysis of ethanol in vitreous humor has been well established. However, studies of drug disposition into vitreous humor are limited. Heart blood, subclavian blood, and vitreous humor specimens from 26 phencyclidine-positive postmortem cases were analyzed to evaluate the distribution of phencyclidine into vitreous humor. Phencyclidine intoxication was not the cause of death in any of the cases analyzed. Specimens were analyzed by solid-phase extraction followed by gas chromatography-mass spectrometry. All positive blood specimens were associated with a positive vitreous humor specimen. On average, the blood phencyclidine concentrations were greater than the vitreous humor phencyclidine concentrations, with average blood/vitreous ratios of 2.85 for heart blood and 2.51 for subclavian blood. However, there was considerable variability between cases, which indicates that although vitreous humor is an appropriate specimen for the detection of phencyclidine in postmortem cases, its interpretative value is limited.