Cotinine is a metabolite of nicotine. Cotinine typically remains in the blood between 48 and 96 hours. The level of cotinine in the blood is proportionate to the amount of exposure to tobacco smoke, so it is a valuable indicator of tobacco smoke exposure, including secondary smoke. Women who smoke menthol cigarettes retain cotinine in the blood for a longer period.^[1] Race may also play a role, as blacks routinely register higher blood cotinine levels than whites.^[2] Several variable factors, such as menthol cigarette preference and puff size, suggest that the explanation for this difference may be more complex than gender or race.

Drug tests can detect cotinine in the blood, urine, or saliva.

The word 'cotinine' is an anagram of 'nicotine'.

*source www.Wikipedia.org