THCV-COOH, a urinary metabolite of a compound found in natural marijuana but absent from synthetic Marinol, was detected only after marijuana use, providing a reliable way to distinguish marijuana from prescription THC in drug tests.
Read this if you are involved in drug testing and need to distinguish between prescription THC and marijuana use.
THCV-COOH was detected only after smoking marijuana, never after Marinol
What the researchers found
Because synthetic THC (Marinol) and natural marijuana produce identical urinary metabolites, drug tests cannot tell them apart. This creates a problem: people testing positive for cannabis can claim they were using a prescription.
Researchers identified a solution: delta-9-tetrahydrocannabivarin (THCV), a natural compound present in marijuana but absent from synthetic Marinol. THCV is metabolized to THCV-COOH, which can be detected in urine.
Four subjects received, in randomized order: oral Marinol (15 mg), smoked THC in a placebo marijuana cigarette (16.88 mg), or smoked marijuana (2.11% THC, 0.12% THCV). Urine was collected for one week.
THCV-COOH was detected only after smoking actual marijuana. Neither oral Marinol nor smoked pure THC produced THCV-COOH in urine. This confirmed THCV-COOH as a reliable marker to distinguish marijuana use from Marinol use.
Why it matters
This study solved a practical problem in drug testing: distinguishing between legal prescription THC and illegal marijuana use. The THCV-COOH marker has since been used in forensic and workplace drug testing when this distinction matters.
The numbers in context
Four subjects, three sessions. Marinol: 15 mg oral. Smoked THC: 16.88 mg. Smoked marijuana: 2.11% THC, 0.12% THCV. Detection limit: 1.0 ng/mL. THCV-COOH only positive after marijuana.
How the study worked
Three-session, within-subject, crossover design with four subjects. Each received oral Marinol, smoked THC in placebo cigarette, and smoked marijuana in randomized order. GC-MS analysis of urine for THC-COOH and THCV-COOH.
What this study cannot tell us
Only four subjects. THCV content varies among marijuana varieties, so very low-THCV marijuana might not produce detectable THCV-COOH. The study predates the availability of many modern cannabis products. Detection window for THCV-COOH may be shorter than for THC-COOH.
How to read the evidence
A controlled crossover study with the strongest possible design for a biomarker validation study, though with only four subjects.
When this study was published
Published in 2001. The THCV marker approach has been adopted in some forensic testing protocols.
The bigger picture
As more patients receive prescription cannabinoids, the ability to distinguish pharmaceutical from botanical cannabis use in drug testing has become increasingly important for workplace, legal, and clinical purposes.
Questions still open
- Does THCV-COOH detection work with edible marijuana as well as smoked? How does THCV content vary across commercial cannabis strains? What is the detection window for THCV-COOH compared to THC-COOH?
Common questions
Can drug tests tell marijuana from prescription THC?
Why does this matter?
Read the original research
Delta9-tetrahydrocannabivarin as a marker for the ingestion of marijuana versus Marinol: results of a clinical study.
Journal of analytical toxicology, 25(7), 565-71
Citation
ElSohly, M A; deWit, H; Wachtel, S R; Feng, S; Murphy, T P. (2001). Delta9-tetrahydrocannabivarin as a marker for the ingestion of marijuana versus Marinol: results of a clinical study.. Journal of analytical toxicology, 25(7), 565-71.
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