nicotine

Nicotine is a potent alkaloid with stimulant effects that occurs naturally in the nightshade family, most prominently in tobacco (Nicotiana tabacum). It is the primary psychoactive component of tobacco products and is used in some insecticides. In the body, nicotine acts on nicotinic acetylcholine receptors in the brain and peripheral nerves, triggering the release of neurotransmitters such as dopamine, norepinephrine, and acetylcholine, which contribute to arousal and reward.

Sources and forms: Nicotine is encountered mainly in smoked and smokeless tobacco products, nicotine replacement therapies (gum, patch, lozenge, spray, inhaler), and electronic cigarettes. The compound is produced by tobacco plants in roots and leaves as a natural pesticide defense; commercial nicotine is also produced synthetically.

Pharmacokinetics: Nicotine is rapidly absorbed, especially via the lungs, and reaches the brain within seconds of inhalation. It is extensively metabolized in the liver by the enzyme CYP2A6 to cotinine. The elimination half-life is about 1–2 hours, which drives repeated use in dependent individuals.

Health effects: Nicotine is addictive and can increase heart rate and blood pressure. It is not the primary cause of cancer in tobacco products, but nicotine may contribute to cardiovascular and reproductive risks. Nicotine replacement therapies, used as smoking cessation aids, are generally safer than smoking when used as directed.

Regulation and research: Governments regulate nicotine-containing products to reduce initiation among youth and to support cessation. The rise of e-cigarettes has raised concerns about youth uptake and safety. Ongoing research investigates potential therapeutic uses of nicotine and the long-term health effects of non-combustible delivery.