Cotinine is produced by the liver during the breakdown of the nicotine present in tobacco. It is then distributed in the blood, urine and saliva. Its dosage therefore makes it possible to assess the smoking of an individual.

Cigarette smoke contains many toxic substances whose deleterious consequences on health are no longer to be demonstrated. Among these substances, nicotine, a powerful psychostimulant, is naturally present in tobacco leaves. She is responsible for the physical addiction to tobacco, which is also associated with psychological addiction. Nicotine is found in cigarette smoke. 70% of inhaled nicotine is absorbed by the body. It crosses the wall of the capillaries of the pulmonary alveoli to enter the bloodstream. It is then transported to the various organs. Its dosage makes it possible to assess smoking. However, it does not stay in the body for very long and disappears from the blood within half a day. It is not measurable in the urine.

Cotinine is produced by the liver when it breaks down nicotine. It represents 20% of the metabolites produced during the elimination of nicotine. Unlike the latter, cotinine remains in the blood at a stable concentration for a long time (16 to 30 hours). It is then evacuated by the urine and present in them up to 48 hours after the last cigarette. This makes it a very good marker to assess an individual’s tobacco consumption, whether active or passive. The cotinine content of the urine reflects the nicotine intake of the previous 2 to 3 days and gives an idea of ​​the amount of tobacco consumed. However, it does not make it possible to assess the intensity of an individual’s tobacco dependence.

Cotinine can also be measured in saliva or in the blood. Its presence in the nails or hair reflects exposure to tobacco over a longer period, up to 3 months.

During pregnancy, cotinine accumulates in the fetus in active smokers as well as in women who smoke secondarily. Smoking increases the risk of miscarriages and perinatal morbidity and mortality. It decreases the chances of having a healthy child, whether it is the woman or the man who smokes. Nicotine also passes into breast milk and is therefore passed on to the child during breastfeeding.

Nicotine being responsible for tobacco addiction, it is interesting to measure it. For this, cotinine is an excellent biological marker of exposure to tobacco, active or passive. Its dosage is reserved for tobacco consultations and medical research.

In the management of smoking cessation, its dosage is useful for quantifying smoking objectively and thus better monitoring and adapting withdrawal. If the patient is taking nicotine replacement therapy, the dosage of cotinine allows the dosage of the treatment to be adjusted. Indeed, like the nicotine inhaled in cigarette smoke, that ingested via gums and chewing gum or even absorbed by the skin via patches can be assessed by the dosage of cotinine. This dosage will be associated with other parameters such as the number of cigarettes smoked per day, the dependence test (Fagerström test) or the measurement of expired carbon monoxide.

In non-smokers, the dosage of cotinine is a reliable marker of passive smoking. It makes it possible to measure its impact, whether family or professional.

A cotinine dosage may be requested by insurance when borrowing for example, in order to assess tobacco consumption which constitutes a risk factor for cardiovascular disease.

The cotinine assay can be done by taking urine, saliva or blood. The urinary cotinine assay is performed on a sample obtained from urination at any time of the day. During the sample, the patient will have to answer a few questions (why this dosage is carried out, which associated drugs, how many cigarettes per day).

In the case of nicotine replacement therapy in the context of smoking cessation, the result of the dosage will allow the doctor to adjust the doses. These will be reduced to follow the cessation while remaining sufficient to prevent withdrawal. The dosage also makes it possible to verify that the patient has indeed stopped smoking and that he is taking his treatment as prescribed.

The cotinine level makes it possible to differentiate the active smoker from the passive smoker.

If you want to quit smoking, talk to your doctor who can help you along the way.