Assays for Cannabinoids

Marijuana use pervades every facet of our daily life. However, despite the growing awareness and mounting fear that marijuana is having a serious impact on driving performance and highway safety, routine analysis for the detection of marijuana use is minimal. Part of this reluctance is due to a lack of understanding about the assays, what the assays can and can not do, and what the results mean. Fortunately, intensive research has been conducted over the past 10 years on the metabolism, disposition, and pharmacokinetics of marijuana, and a variety of analytical methods have been developed to detect and measure cannabinoids and/or their metabolites in blood, urine, and other biological materials. In this paper I review these analytical methods and recent studies designed to evaluate their performance, the suitability of cutoff levels, and the compatability of screening methods and confirmation procedures. Further, I discuss the interpretation of results, the question of intoxication, passive inhalation, and oral ingestion, and describe a scheme used in the workplace, with inexpensive urine tests to select blood specimens.