Philip M. Kemp

Acute Marihuana (THC) Exposure Produces a “Transient” Topographic Quantitative EEG Profile Identical to the “Persistent” Profile Seen in Chronic Heavy Users

In two published pilot studies and a controlled replication using screened normals, chronic marihuana (THC) use was associated with a unique topographic quantitative EEG profile, consisting of significant elevations of Absolute and Relative Power and Coherence of alpha activity over the bilateral frontal cortex as well as a significant decrease in alpha frequency. This report attempts to establish the causal influence of THC in the above findings by the transient production of this exact quantitative EEG profile in subjects who did not display it at the beginning. Using paced smoking of marihuana with high and low dose THC content and placebo marihuana in a counterbalanced design under double blind conditions, all four of the topographic features of chronic THC exposure were produced as transient effects by THC but not by placebo.

Screening Postmortem Whole Blood for Oxycodone by ELISA Response Ratios

The objective of this study was to investigate the accuracy of screening postmortem whole blood for oxycodone using the ratio of the oxycodone immunoassay response to the response for the specimen obtained with a general opiate-class immunoassay. Fifty eight specimens which were negative for opiates and 158 postmortem whole blood specimens positive for opiates including 66 specimens known to contain oxycodone were assayed. Specimens were diluted 1:5 with assay buffer and analyzed by both the Neogen Oxymorphone/Oxycodone ELISA and the Neogen Opiate Group ELISA (Neogen Corporation, Lexington KY). The oxycodone equivalents in ng/mL from the Oxymorphone/Oxycodone ELISA were divided by the morphine equivalents in ng/mL from the Opiates ELISA to obtain an Oxycodone/Opiates Response Ratio. This ratio was compared with the GC/MS data for all specimens and for opiate positive specimens. Receiver Operating Characteristic (ROC) analysis suggested that optimum relative response ratio was 2.0. The sensitivity of the ELISA response ratio for the presence of oxycodone at a response ratio cutoff of 2.0 was 89.4% +/- 3.8% and the specificity was 88.1% +/- 3.2%. Specimens with a ratio of 2.0 or higher had a greater than 50% probability (positive predictive value) of containing oxycodone in a population with a greater than 15% prevalence of oxycodone.