[UPDATED and bumped: Paul Armentano joins me on Today's Stash to discuss this study. Other notable findings are that one's THC-COOH levels do not decline in a linear fashion and that even during long periods of abstinence, you can actually test positive even after a series of negative tests. They even found that for heavy smokers, THC-COOH levels don't reach their peak until a few days into the period of abstinence, and some even tested positive 25 days into abstinence!
In other words, if you quit toking on Saturday, you peed negative on Monday, Tuesday, Wednesday, and Thursday, and then you pee positive on a Friday, it doesn't mean you started toking again during the week. This will be a critical point for defense attorneys to make to a court when a prosecutor claims a probationer's positive urine screen means he's started using marijuana again.]
Every Stasher knows that cannabis is the worst drug there is… when it comes to passing a drug test!
When your school or employer tests your urine for drugs, they aren’t actually detecting THC in your system. (THC, of course, is the psychoactive ingredient in pot that gives you the “high”.) What they are detecting is the presence of inactive marijuana metabolites, known scientifically as THC-COOH, or carboxy THC. The presence of these metabolites in your system do not mean that you are “high”; they mean that you have been “high” sometime in the past, from hours to days to even a week or two.
This is why we at NORML fight so much against urine screening to detect drug impairment, because most cannabis consumers who would test positive for THC-COOH aren’t impaired at the time of testing. Most of us are responsible consumers who might smoke a joint in the evening to relax or on the weekend to unwind, but we never would come to work impaired on cannabis, any moreso than your average weekend beer drinker would down a six-pack and a couple of shots before clocking in. Firing someone for THC-COOH in their system because you think they’re stoned on the job is a bit like firing someone for having a bottle opener on their keychain because you think they’re drunk on the job.
Now, new research from the National Institutes on Drug Abuse (NIDA) delves into exactly how long it takes regular cannabis consumers to produce both positive and negative urine screens.
An important issue for drug-testing programs is the ability to distinguish recent cannabis use from residual drug excretion. Exceptionally long detection times have been reported for cannabinoid metabolites in the urine of frequent drug users during abstinence. During the terminal elimination phase, an individual may produce consecutive specimens that test positive, negative, and positive again over time. This makes interpretation of cannabinoid urine drug test results difficult if it is necessary to determine whether positive results are indicative of new drug use or reflective of previous cannabis exposure.
Data were divided into three groups, 0–50, 51–150, and > 150 ng/mg, based on the creatinine corrected initial THCCOOH concentration. There were statistically significant correlations between groups and number of days until first negative and last positive urine specimens; mean number of days were 0.6 and 4.3, 3.2 and 9.7, and 4.7 and 15.4 days, respectively, for the three groups. These data provide guidelines for interpreting urine cannabinoid test results and suggest appropriate detection windows for differentiating new cannabis use from residual drug excretion.
Or in plain English, if you’re a light smoker, you need about five days to piss clean, a moderate smoker needs about ten days, and a heavy smoker needs fifteen days. Your mileage may vary based on what you smoke, how you smoke, when you smoke, what you weigh, how much fluid you drink, what you eat, and your own unique body chemistry, so if I were you, I’d double those figures. (And if you were me, you’d tell your employer you pee for enjoyment, not for employment, but I understand that not everyone is in such an enviable position.)
The study, “Urinary Elimination of 11-Nor-9-Carboxy-?9-tetrahydrocannnabinol in Cannabis Users During Continuously Monitored Abstinence”, appears in the October 2008 issue of the Journal of Analytical Toxicology.