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Carboxy-THC: how much in plasma (ng/ml) typically results in impairment?

So we're talking about marijuana here, and I've seen different answers, but my brain shuts down with the science.

What kind of impairments would likely result?
How long after smoking are you likely to have significant levels in the blood?
Are carboxy-THC and THC-COOH the same thing?
What kind of carboxy-THC/THC-COOH levels would a chronic user have in the blood?

muffinprincess asked in Science & Math 7 months ago | Report

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  • Labcoat_small
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    Danger

    There are a lot of questions here.

    First of all, -COOH is chemical shorthand for a carboxyl group, so yes, they are the same thing.

    As for the amount of THC and THC-COOH in chronic users and the rate at which detection declines see these graphs:

     

    1) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3159863/figure/F2/

    2) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2784185/figure/F1/

    The first shows the decline of THC levels in patient plasma during a 7 day abstinence.The second a larger sample group under similar conditions.

    The important thing to understand is that THC-COOH is the byproduct of THC metabolism in the body after release from tissues. This ratio of THC/THC-COOH can be used as a measure of the rate at which THC is removed from the blood.

    As for what levels will result in impairment, that is a complicated question. First you have to define impairment, then take in to account the fact that everyone has a different physiology (body size, metabolism, whether or not you are accustomed to cannabinoids) and finally that this sort of question isn't easy to study. It isn't scientifically ethical to tell people to light up and then see how well they drive for instance.

    Here is one paper I found that gives an idea of limits(3):

    "Limited epidemiological studies indicate that serum concentrations of THC below 10 ng/ml are not associated with an elevated accident risk. A comparison of meta-analyses of experimental studies on the impairment of driving-relevant skills by alcohol or cannabis suggests that a THC concentration in the serum of 7-10 ng/ml is correlated with an impairment comparable to that caused by a blood alcohol concentration (BAC) of 0.05%."

    You're final question about how long it takes for THC to be detectable is really going to depend on the same physiology variables I mentioned above. It also depends HEAVILY on how much you smoke and I can't quickly find much information on it.

    I did, however, find a study where the injected a pig with massive amount of THC and looked at how it was distributed throughout the body(4). Crazy.

     

    1) Implications of plasma Delta9-tetrahydrocannabinol, 11-hydroxy-THC, and 11-nor-9-carboxy-THC concentrations in chronic cannabis smokers.
    Karschner EL, Schwilke EW, Lowe RH, Darwin WD, Herning RI, Cadet JL, Huestis MA.
    J Anal Toxicol. 2009 Oct;33(8):469-77.

    2) Do Delta9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users?
    Karschner EL, Schwilke EW, Lowe RH, Darwin WD, Pope HG, Herning R, Cadet JL, Huestis MA.
    Addiction. 2009 Dec;104(12):2041-8. Epub 2009 Oct 5.

    3) A study investigating the acute dose-response effects of 13 mg and 17 mg Delta 9- tetrahydrocannabinol on cognitive-motor skills, subjective and autonomic measures in regular users of marijuana.
    Weinstein A, Brickner O, Lerman H, Greemland M, Bloch M, Lester H, Chisin R, Sarne Y, Mechoulam R, Bar-Hamburger R, Freedman N, Even-Sapir E.
    J Psychopharmacol. 2008 Jun;22(4):441-51.

    4) Postmortem redistribution of THC in the pig.
    Brunet B, Hauet T, Hébrard W, Papet Y, Mauco G, Mura P.
    Int J Legal Med. 2010 Nov;124(6):543-9. Epub 2010 Jan 7.

     

    ps. Please forgive spelling/grammar errors. I'm writing this on the quick.

    pps. "J Anal Toxicol" heh.

    Danger answered in Science & Math 7 months ago | Report
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