Tobacco

Pharmacology of Nicotine

Nicotine is a naturally occurring chemical found in the tobacco plant. It absorbs easily through the lungs, the lining of the mouth, the skin, and, to a lesser extent, the gastrointestinal tract. Nicotine quickly distributes through the bloodstream and easily crosses the blood-brain barrier, allowing it to act directly on the brain. The dose and bioavailability of nicotine (fraction of administered dose reaching systemic circulation unchanged) depends on the method by which nicotine is delivered to the body.

The average cigarette contains 6 to 11 milligrams (mg) of pure nicotine of which only a fraction, 1 to 3 mg, enters into the bloodstream. The bioavailability of nicotine can be increased up to threefold depending on the inhalation technique of the smoker. In comparison, the nicotine absorbed from the average dose of smokeless tobacco is equivalent to three to four cigarettes.

Nicotine from tobacco smoke is quickly absorbed through the lungs and distributed throughout the body. It is estimated that nicotine from smoked tobacco reaches the brain within seven seconds of inhalation. The nicotine found in smokeless tobacco is absorbed through the buccal membranes of the mouth and through the small intestine if tobacco juices are swallowed. Although both smoked tobacco and smokeless tobacco have similar peak concentrations in the venous blood, the absorption of nicotine from smokeless tobacco occurs much more slowly than that of smoked tobacco. Consequently, smokeless tobacco has a longer duration of effect which may persist for some time after the tobacco is removed.

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