Delta(9)-Tetrahydrocannabivarin testing may not have the sensitivity to detect marijuana use among individuals ingesting dronabinol

The purpose of this Study was to determine whether Delta(9)-tetrahydrocannabivarin (THCV), a plant cannabinoid, is a sensitive measure to detect recent marijuana use in cannabis dependent patients. It has been purported that smoking an illicit plant cannabis product will result in a positive THCV urinalysis, whereas the oral ingestion of therapeutic THC such as dronabinol will result in a negative THCV urinalysis, allowing for discrimination between pharmaceutical THC products and illicit marijuana products. In a double-blind placebo-controlled trial to determine the efficacy of dronabinol in cannabis dependence, all 117 patients produced a positive urine for the marijuana metabolite 11-nor-Delta(9)-THC-9-carboxylic acid: THC-COOH, but 50% had an undetectable (<1 ng/ml) THCV-COOH test. This suggests that THCV may not be a sensitive enough measure to detect recent marijuana use in all heavy marijuana users or that its absence may not discriminate between illicit marijuana use and oral ingestion of THC products such as dronabinol. We propose that the lack of THCV detection may be due to the variability of available cannabis strains smoked by marijuana users in community settings. (C) 2009 Elsevier Ireland Ltd. All rights reserved.