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General information on nicotine

Nicotine is a stimulant drug which is found in the nightshade family of plants which include the tobacco plant. This drug is highly addictive and leads to dependence of tobacco products and can cause moderate to severe symptoms on withdrawal of tobacco.

How is nicotine absorbed by the body?

Nicotine is rapidly absorbed by the body via the bloodstream and can reach the brain within 10-20 seconds after inhalation of tobacco smoke. The amount of nicotine which is absorbed by the body depends on factors such as how much smoke is inhaled, what type of tobacco is used and whether a filter is utilized or not.

Nicotine is then metabolized by the liver and one of the active metabolites which is found in the blood stream and then excreted via the urine is cotinine. The elimination half-life of nicotine is 2 hours which means that half of the effect of nicotine on the body is lost after this time. It's important to take note though, that in long-term smokers, this half life will increase due to accumulation of nicotine in body tissue. In this scenario the elimination half-life increases to 11 hours.

How are nicotine levels measured in the body?

Nicotine in the body is measured by checking blood levels, saliva and or urine of an individual for the mentioned active metabolite, cotinine. This test is done for life insurance and work related purposes. Cotinine can also be found in hair and nail samples but these are never used for testing as cotinine can be present from tobacco used many months previously.

A common question is how long cotinine can be detected in the human body and the answer to that question is, it depends. As mentioned, certain factors determine the rate of absorption and accumulation of nicotine in the body.

Other factors, including those mentioned above, which can affect the duration of cotinine in the body are as follows:

  • Gender - women tend to clear cotinine faster than men do.
  • Race - studies show that blacks tend to have a lower clearance of cotinine than whites. Asians also had decreased cotinine clearances compared to whites.
  • Renal and liver related diseases - metabolism and excretion rates are reduced, therefore cotinine levels will be higher when measured.
  • Pregnancy - cotinine clearance is elevated in this scenario.


Issues that need to be considered when checking for cotinine levels are, firstly, that the patient being tested is well aware of their rights when having this test done. They have the right to be informed correctly as to why the test is being done and how the test will be performed. The individual in question also needs to understand that a positive result may result in a job application or life insurance policy being denied.

It's also very important to take note that cotinine levels can be tested positive due to second-hand tobacco smoke inhalation. It's very important then that one should try and avoid this exposure, especially when it's known that the test will be done in the near future. 

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