nicotin

Nicotine, the alkaloid most people associate with tobacco, is a naturally occurring compound found predominantly in tobacco plants (Nicotiana tabacum). Its molecular formula is C10H14N2 and its molecular weight is about 162.23 g/mol. The term nicotin is used in some languages for the same substance. Nicotine is also present in smaller amounts in other Nicotiana species and related plants in the nightshade family. The compound can be absorbed through the lungs, oral mucosa, and skin and crosses the blood-brain barrier rapidly.

Nicotine acts as an agonist at nicotinic acetylcholine receptors in the central nervous system and autonomic ganglia, leading to the release of neurotransmitters such as dopamine, norepinephrine, acetylcholine, and serotonin, which produces increased alertness and mood modulation. It is highly addictive due to its reinforcing effects. Nicotine is metabolized primarily in the liver to cotinine, which has a longer half-life (about 16 hours) and is commonly measured to assess exposure. The half-life of nicotine itself is about 2 hours.

Nicotine is a major component of tobacco products, including cigarettes, cigars, smokeless tobacco, and vaping liquids. It is also used in nicotine replacement therapies (gum, patch, lozenges, nasal spray) to aid smoking cessation. Historically, nicotine and related alkaloids were used as insecticides; modern use is regulated due to safety concerns.

Health and regulation: Health effects of tobacco use are driven by many toxicants in smoke, but nicotine contributes to addiction and cardiovascular stimulation. Nicotine itself is not classified as a carcinogen by most authorities, though it may promote tumor progression in some contexts. Regulation varies by country, with age limits, product labeling, and restrictions on nicotine content and sales in many jurisdictions. Safety guidelines emphasize avoiding accidental ingestion or exposure, especially by children.