Cotinine is the metabolite of nicotine, produced by the body after exposure to nicotine, a chemical commonly found in tobacco. High cotinine levels will be found in smokers. People who are exposed to secondhand smoke for a long period of time will also have increased cotinine levels in their body.
Cotinine is formed as a major metabolite of nicotine after tobacco smoking. The average half-life of cotinine is 19 hours.
It can be detected in plasma, urine, and saliva. Cotinine is also formed in the body after intake of some vegetables (e.g., eggplant, tomato, and green pepper) primarily of the family solanaceae. These vegetables contain nicotine as their natural defense mechanism against fungi, bacteria, insects, and animals.