Understanding Cotinine
The term “COT” on a drug test stands for Cotinine, which is the primary metabolite of nicotine. When nicotine, found in tobacco and e-cigarette products, enters the body, it is processed primarily by the liver. The liver enzyme cytochrome P450 2A6 converts nicotine into Cotinine, which is then eliminated through the kidneys in the urine. Cotinine’s presence is a direct chemical indicator of recent exposure to nicotine from any source, including cigarettes, vapes, and nicotine replacement therapies.
Testing focuses on Cotinine rather than nicotine because of the significant difference in their half-lives. Nicotine is rapidly metabolized, with a half-life of only one to four hours, meaning it quickly disappears from the bloodstream. In contrast, Cotinine has a much longer half-life, typically ranging from 16 to 20 hours, and sometimes up to 40 hours. This extended presence makes Cotinine a more stable and reliable biomarker for confirming nicotine exposure over a longer period.
The Mechanics of Cotinine Testing
Cotinine testing is commonly performed using biological samples, with urine and saliva being the most frequent choices for workplace or insurance screening. Urine testing is favored because Cotinine concentrations are typically four to six times higher than in saliva or blood, offering a wide detection range. Saliva testing is popular due to its non-invasive collection method and can detect exposure for up to four days. Blood and hair samples are less common; hair testing provides a window into long-term exposure spanning several months.
The result of a Cotinine test is determined by comparing the measured concentration, expressed in nanograms per milliliter (ng/mL), to a specific “cutoff level.” This cutoff is a predetermined quantitative threshold set by the testing laboratory. For example, a common urinary cutoff may range from 50 to 200 ng/mL, while salivary cutoffs are often lower (10 to 20 ng/mL). A result above the cutoff is reported as positive, while a result below it is reported as negative, even if Cotinine is detected at a low level. The cutoff differentiates between active nicotine use and minor, passive exposure, such as secondhand smoke, which usually results in levels below the threshold.
Detection Windows and Clearance Time
The length of time Cotinine remains detectable varies significantly based on the sample type and the individual’s metabolic rate. Due to Cotinine’s half-life of 16 to 20 hours, the body typically clears most of the chemical within eight to ten days after the last nicotine exposure. In urine, Cotinine is generally detectable for up to three to four days after cessation, though traces may persist for a week or more in heavy users. Saliva testing offers a slightly shorter window, usually up to four days.
For long-term monitoring, hair follicle testing provides the widest detection window. Cotinine can be detected in hair for up to three months, reflecting a history of use. Clearance time is not uniform for everyone; factors like the frequency and amount of nicotine use, hydration levels, and genetic differences in liver metabolism affect how quickly Cotinine is eliminated.