Nicotine is a widely used alkaloid stimulant and that is naturally produced in the nightshade family of plants (most notably in tobacco). It is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits (nAChRα9 and nAChRα10) where it acts as a receptor antagonist. Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. Nicotine is also present at concentrations of millionths of a percent in the edible family Solanaceae, including potatoes, tomatoes, and eggplants, though sources disagree on whether this has any biological significance to human consumers. It functions as an antiherbivore chemical; consequently, nicotine was widely used as an insecticide in the past , and neonicotinoids, such as imidacloprid, are widely used.
Nicotine use as a tool for quitting smoking has a good safety history. Nicotine itself is associated with some health harms. Nicotine is potentially harmful to non-users. At low amounts, it has a mild analgesic effect. The Surgeon General of the United States indicates that nicotine does not cause cancer. Nicotine has been shown to produce birth defects in some animal species, but not others. It is considered a teratogen.
Nicotine addiction may not appear as harmful as many other addictions. This is likely because tobacco products are legal and easy to get, and the worst side effects of abusing them take time to develop. Tobacco use claims more lives than any other addictive substance. Many smokers cannot quit despite knowing smoking’s impact on their health. Wanting to quit but being unable to is a telltale sign of addiction