Hedons

This is probably the single most asked question on this forum and there is no set answer and no equation that will allow us to calculate the answer even if we know your height, weight, metabolism, frequency of marijuana use, potency of marijuana taken, etc.

When marijauna is taken over a period of time, accumulation of the drug or its metabolites may occur if elimination of the drug or metabolites is not complete in the interval between doses.

For chronic and heavy marijuana users (cannabis use daily or more often for periods of several months), it has been reported that the marijuana metabolites were detectable in the urine with EMIT-d.a.u. at 20 ng/ml for an average of 31 days with a range of 4-77 days of abstinence (Ellis et al. 1985),

An individual who smokes regularly even as few as two or three times a week will generally have marijuana-positive urines most of the time. A heavy (daily for months at least), chronic smoker who stops smoking may continue to produce positive samples for longer than a month (depending on the assay cutoff) because of the amount of THC accumulated in the body. It becomes difficult, therefore, to distinguish between the chronic smoker who may in fact have stopped smoking weeks before from the smoker who has not.


For light users (cannabis use weekly or less often), it is detectable for an average of 13 days with a range of 3-29 days. Due to the individual variations, substantial overlap occurs in the ranges observed. As explained in the multicompartment model for THC, THC is sequestered in tissues (deep compartment), and the rate of elimination of THC from the body is limited by the slow release of THC from this “tissue compartment.” As substantial amounts of THC can be accumulated in tissues for chronic users, considerably long times are required to eliminate it. Consequently, a positive analysis for THC metabolite in urine at these concentration levels may indicate last time marijuana use of a few hours to as much as a few weeks previously.

Assuming that screening assays of 50 ng/ml cutoff and confirmation assays for 9-carboxy-THC of about 10-15 ng/ml are used, urine samples will generally be positive for 1 to 3 days.


Excerpt taken from
Urine Testing for Drugs of Abuse
Editors:Richard L. Hawks, Ph.D., C. Nora Chiang, Ph.D., Division of Preclinical Research
National Institute on Drug Abuse
NIDA Research Monograph 73, 1986
DEPARTMENT OF HEALTH AND HUMAN SERVICES


Ellis, G.M., Jr.; Mann, M.A.; Judson, B.A.; Schramm, N.T.; and Tashchian, A.
Excretion patterns of cannabinoid metabolites after last use in a group of
chronic users. Clin Pharmacol Ther 38:572-578, 1985.

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