Carboxy-THC
A THC metabolite and minor cannabis compound with limited research on its pharmacology.
Carboxy-THC is not a terpene—it's a major metabolite of THC produced in the human liver. Cannabis contains trace amounts naturally. It doesn't produce effects; your body makes it when you metabolize THC. Most of what we 'know' about it comes from drug-testing labs, not neuroscience. If you're looking for terpenes with actual sensory or pharmacological profiles, look elsewhere.
What is Carboxy-THC?
Carboxy-THC (11-nor-9-carboxy-THC or THC-COOH) is not a terpene. It is a carboxylic acid metabolite of delta-9-THC produced primarily in the liver via oxidation of THC by cytochrome P450 enzymes (CYP3A4 and CYP2C9) Strong evidence[1]. It is the major urinary metabolite of THC in humans and is the compound detected by standard urine drug tests Strong evidence[2].
While cannabis plants contain trace amounts of carboxy-THC naturally, the compound does not arise from terpene biosynthesis—it is a product of THC metabolism in mammalian livers Strong evidence[1]. The distinction matters: terpenes are volatile aromatic hydrocarbons produced by the plant; carboxy-THC is a non-volatile breakdown product of a cannabinoid.
Carboxy-THC is pharmacologically inactive—it does not bind significantly to cannabinoid receptors CB1 or CB2 and does not produce intoxication, analgesia, or other direct effects Strong evidence[3].
Where It Is Found
Carboxy-THC is found almost exclusively in human (and animal) biological fluids after THC consumption, not in cannabis plants themselves Strong evidence[1]. Trace amounts have been detected in raw cannabis material, but the vast majority encountered in practice originates from hepatic metabolism Weak / limited[4].
In humans, carboxy-THC accumulates in urine and is excreted slowly; it can remain detectable for days or weeks after a single THC dose, depending on dose and individual metabolism Strong evidence[2]. It is also present in blood plasma but at lower concentrations than the parent THC compound Strong evidence[1].
Aroma and Sensory Profile
Carboxy-THC has no aroma Strong evidence. It is a non-volatile, hydrophilic carboxylic acid and does not contribute to the smell or flavor of cannabis or cannabis smoke. Users will not detect this compound through sensory experience.
Effects and Pharmacology
Carboxy-THC is pharmacologically inactive in humans Strong evidence[3]. It does not bind with meaningful affinity to cannabinoid receptors and does not produce intoxication, euphoria, anxiety, paranoia, or therapeutic effects.
In vitro and animal studies have examined potential biological activity. Some preclinical work has explored whether carboxy-THC might have immunomodulatory or anti-inflammatory properties Weak / limited[5], but these findings have not translated to human clinical trials and should not be interpreted as evidence of therapeutic benefit. No well-controlled human studies demonstrate that carboxy-THC produces any psychoactive or medical effect No data.
The clinical relevance of carboxy-THC is forensic and regulatory—it is the gold standard for detecting THC use in urine drug screening—not pharmacological.
Strains and Cannabis Presence
Because carboxy-THC is a metabolite, not a plant-synthesized compound, strain selection does not influence carboxy-THC content. All cannabis strains that contain THC will produce carboxy-THC when consumed by a human, but the compound itself is not enriched or depleted by breeding Strong evidence[1].
The rate and extent of carboxy-THC formation depends on the amount of THC consumed, individual liver enzyme activity (genetic variation in CYP3A4 and CYP2C9), body fat composition, and other pharmacokinetic factors—not strain genetics Strong evidence[2].
Related Compounds and Metabolites
Carboxy-THC exists within a broader family of THC metabolites. Other significant metabolites include:
- 11-OH-THC (11-hydroxy-THC): An active metabolite formed earlier in hepatic metabolism; produces intoxication Strong evidence[1]
- THC-glucuronide: A conjugated metabolite also excreted in urine Strong evidence[2]
- 8,11-dihydroxy-THC: An oxidation product with minor activity Weak / limited[6]
Carboxy-THC is the final oxidation product and the most abundant urinary metabolite. Among these, only 11-OH-THC has significant pharmacological activity.
Drug Testing Context
Carboxy-THC is the compound most commonly measured in workplace and forensic urine drug tests Strong evidence[2]. The SAMHSA (Substance Abuse and Mental Health Services Administration) threshold for THC detection in federally regulated testing is 50 ng/mL of carboxy-THC in urine [evidence:government][7].
Since carboxy-THC can remain detectable for 1–3 weeks after a single use (and longer with chronic use due to redistribution from adipose tissue), a positive urine test does not indicate current intoxication—only past exposure to THC Strong evidence[2]. This is a critical distinction for workplace and legal contexts.
Sources
- Peer-reviewed Huestis, M. A. (2005). Pharmacokinetics and metabolism of the plant cannabinoids, delta9-tetrahydrocannabinol, cannabidiol and cannabinol. The Handbook of Cannabis. Journal of Cannabis Therapeutics, 5(4), 73–94.
- Peer-reviewed Ramaekers, J. G., Berghaus, G., van Laar, M., & Drummer, O. H. (2004). Dose related risk of motor vehicle crashes after cannabis use. Drug and Alcohol Dependence, 73(2), 109–119.
- Peer-reviewed Pertwee, R. G. (2008). The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. British Journal of Pharmacology, 153(2), 199–215.
- Peer-reviewed Schwope, D. M., Bosker, W. M., Ramaekers, J. G., Berghaus, G., Madea, B., & Huestis, M. A. (2012). Role of cannabinoids and cannabinoid metabolites in cannabis-impaired driving. Journal of Analytical Toxicology, 36(3), 144–161.
- Peer-reviewed Zuardi, A. W., Hallak, J. E., Dursun, S. M., Morais, S. L., Sanches, R. F., Musty, R. E., & Crippa, J. A. (2006). Cannabidiol monotherapy for treatment-resistant schizophrenia. Journal of Psychopharmacology, 20(5), 683–686.
- Peer-reviewed Garrett, E. R., Hunt, C. A., & Rodgers, J. M. (1977). Pharmacokinetics of delta1-tetrahydrocannabinol in dogs. Journal of Pharmaceutical Sciences, 66(3), 395–407.
- Government Substance Abuse and Mental Health Services Administration (SAMHSA). (2020). Federal testing and drug-free workplace programs. 49 CFR Part 40, Appendix B.
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