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. Therefore, the presence of a drug metabolite can be a reliable indicator that a person used the “parent” drug of that metabolite.
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.
Here are some examples of drug test kits that detect metabolites, rather than the parent drug:
A typical cocaine drug test kit looks for the presence of the metabolite benzoylecgonine. 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).
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.
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.