The current method for detection of marijuana use measures 11-nor-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC), the major metabolite of THC in a person’s urine. However, commercially available CBD products sold without purity regulations often contain trace tetrahydrocannabinol. Long-term or high dose use of CBD products can result in tetrahydrocannabinol exposures, potentially producing a positive marijuana drug test. These results are not false positives since marijuana biomarkers are present, but inaccurately identify donors as marijuana users. To address this problem, scientists at the MedTox Laboratories developed an assay that discriminates marijuana use from the use of CBD contaminated with tetrahydrocannabinol.
This assay measures the urine concentration of THC, CBD, 11-COOH-THC, and 7-carboxy-cannabidiol (7-COOH-CBD), the main metabolite of CBD. When this assay was applied to urine samples from trusted donors known to use CBD products but completely abstain from marijuana, no THC was detected but 11-COOH-THC was detected besides CBD and 7-COOH-CBD. However, the concentration of 11-COOH-THC was always at least five-time lower than that of 7-COOH-CBD.
Next, the researchers applied this assay to urine samples from donors who claimed to use CBD with unknown marijuana use history. Results from assay allowed classification of these donors into three groups: CBD use without marijuana, definite marijuana, and indeterminate state of mixed CBD and THC use. Those sorted into the CBD group had CBD/THC concentration ratio of >10 and generally a higher 7-COOH-CBD than 11-COOH-THC concentration. Notably, some donors in the CBD group had a 11-COOH-THC concentration larger than 15ng/ml, which is the threshold for a positive marijuana drug test, as a result of their consistent use of commercial CBD products.
These findings highlight that the current method for marijuana drug test, which measures only 11-COOH-THC, can misidentify consistent CBD users as marijuana users. The newly developed assay, in contrast, can distinguish marijuana consumption from tetrahydrocannabinol exposure from contaminated CBD use.