Marijuana drug testing
For medical marijuana patients, drug testing can be one of the most troublesome problems they must face. Drug urine screening has become the norm in the American workplace in the past few years. It’s also being used as a test for driving under the influence in a few states, but there’s no good scientific justification behind that practice.
Easily the most widely used and objectionable type of drug testing is urinalysis. Unfortunately, urine tests are particularly oversensitive to marijuana because traces can be detected for days or weeks after the most recent use. Heroin, methamphetamine, cocaine, and even alcohol have much shorter detection times than marijuana. In fact, alcohol is barely detectable in urine and is rarely screened for in workplace drug programs.
Urine tests do not detect if someone is actually under marijuana’s influence. That’s mostly because they don’t measure THC, but, instead, non-psychoactive cannabinoid metabolites that are created in the liver and linger throughout the system long after the effects of THC have completely died down. These tests detect a substance called THC-COOH (11-nor-9-carboxy-THC). Although it is sometimes referred to as an acid, it should not be confused with THC acid—a precursor to THC found in the actual plant.
THC-COOH isn’t psychoactive, but some evidence suggests that it could have analgesic and anti-inflammatory properties (Burnstein). THC-COOH levels accumulate steadily in the urine for the first couple of hours after smoking. Then it will gradually decrease over a period of days for occasional users. Frequent users should note that THC-COOH will stay in their systems for up to a few weeks because the cannabinoids and metabolites accumulate in their body fat over time. There is literally no evidence that correlates levels of THC-COOH in urine with a concurrent state of intoxication. THC-COOH’s presence (and that of other metabolites) merely indicates that substantial metabolic degradation has already begun in the body.
Because of this, urine tests are practically incapable of making a distinction between occasional, weekend use and on-the-job use or impairment. The US Department of Justice even admits that “a positive test result, even when confirmed…does not indicate abuse or addiction, recency, frequency, amount of use, or impairment,” (DOJ). Despite this, the prevalence of unreliable urine testing has not waned.
This is all compounded by the fact that frequent and infrequent marijuana users metabolize THC in very much the same way—a fact that leads to many misinterpretations. Another frequently overlooked fact is that a majority of the absorbed THC is discharged in feces. Indeed, only about 33 percent of the THC gets eliminated in the urine. Fortunately, drug testing companies have not found it worth their while to promote excrement testing.