Cotinine (nicotine)

Cotinine is an alkaloid found in tobacco and is the primary metabolite of nicotine. After nicotine is absorbed into the bloodstream, it is largely metabolized by the liver into cotinine. Because cotinine has a significantly longer half-life than nicotine, remaining detectable in the body for several days, it serves as a reliable and stable biomarker for nicotine exposure. This makes it particularly useful for assessing recent tobacco use, including cigarettes, cigars, pipes, and smokeless tobacco, as well as exposure to secondhand smoke. Cotinine levels can be measured in various bodily fluids, including urine, blood, and saliva.