It may come as a surprise that some drug test kits don’t actually detect the drug named on the kit. Instead, the kits detect one or more metabolites of the drug. The presence of a drug metabolite is a reliable indicator that a person used the “parent” drug of that metabolite.
A drug metabolite is a byproduct of the body breaking down, or “metabolizing,” a drug into a different substance. The process of metabolizing a drug is predictable and certain; everyone metabolizes drugs the same way. Some metabolites stay in the body much longer than the parent drug. When that is the case, a drug test has a higher probability of identifying a drug user by looking for the metabolites of the drug, rather than the parent drug.
Cotinine tests are one of the only tests that manufacturers label for the metabolite being detected, rather than for the parent drug. About every other drug of abuse test is named for the parent drug, even when the kit detects metabolites. And because we don’t believe that everyone knows that cotinine is the primary metabolite of nicotine, we follow the same convention by marketing cotinine tests as nicotine tests.
Here are some examples of drug test kits that detect metabolites, rather than the parent drug:
Nicotine is metabolized into cotinine, which has a much longer life in the body than the parent nicotine drug. Therefore, a urine drug test for “nicotine” looks for the presence of cotinine as an indicator of tobacco use.
A typical cocaine drug test kit looks for the presence of benzoylecgonine, the primary metabolite of cocaine. The presence of benzoylecgonine in a person’s system indicates cocaine use. Benzoylecgonine stays in a person’s system significantly longer than cocaine (the “parent” drug).
THC is the active substance in marijuana. However, the body quickly metabolizes the THC molecule into several metabolites with long chemical names. Urine drug tests typically detect the THC-COOH (nor-delta-9-tetrahydrocannabinol) metabolite to identify marijuana users because it stays in the body much longer than the parent THC drug.
However the THC-COOH metabolite does not appear in oral fluid. Therefore an oral fluid marijuana test must detect the parent THC drug.