Nicotine has a range of physiological effects and has provided researchers with an opportunity to learn nervous system function. It is readily absorbed through the skin and lungs, but because it is a strong base is not well absorbed in the acidic environment of the stomach. Nicotine travels from the lungs to the brain in about 7 seconds, thus each puff produces a reinforcing effect. The positive effects of nicotine are associated with a complex balance of stimulation and relaxation. For example, depending on the dose, it can increase or decrease the heart rate. One of the most prominent reactions of first-time users is nausea and vomiting. This reaction is due to stimulation of both the central and peripheral nervous systems, which triggers a vomiting reaction. The underlying mechanism of action is its effect on acetylcholine-like receptors, sometimes referred to as nicotinic receptors.


Nicotine is metabolized in the liver, lung, and kidney. It has a relatively short half-life of about 2 hours, which greatly contributes to the desire to have another smoke in an effort to restore blood nicotine levels. The primary metabolite of nicotine is cotinine, which has a much longer half-life than nicotine. Because of cotinine's longer half-life, insurance companies will typically test urine or blood samples for cotinine to determine if someone has been smoking. Nicotine and its metabolites are readily excreted in the urine. Nicotine is also excreted in the breast milk of nursing mothers, with heavy smokers having up to 0.5 mg of nicotine per liter of milk. Given the infant's small size, this can represent a significant dose of nicotine for the baby.

The skin absorption of nicotine and subsequent adverse effects make it an effective pesticide. Nicotine poisoning occurs primarily from children coming in contact with nicotine insecticides or tobacco products.

Next: Nicotine - Health Effects and Regulation

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