ABSTRACT
Tobacco, a New World plant, spread to Europe and Asia only after the discovery of the Americas. Its addicting ingredient, nicotine, was isolated in 1828. Although nicotine is quite poisonous to insects in the larval and pupal stages, it currently has no medicinal use. Tobacco may be chewed or insufflated into the nose as snuff, with absorption by both routes, but the most popular method of use by far is combustion just outside the lips with subsequent inhalation of the nicotine-laden smoke. Nicotine is absorbed through the mouth, nasopharynx, gastrointestinal, and pulmonary mucosa essentially completely because of its high water solubility and pKa of 8.5. At acid pH it is largely ionized and not absorbed, but in the small intestine, where more alkaline conditions occur, it is readily taken into the body. It is known that pulmonary absorption from inhalation of nicotine-laden smoke is as rapid as i.v. injection with substantial blood levels reached 10–15 s after the first inhalation. A single cigarette contains about 20 mg of nicotine, of which less than 1 mg is delivered in smoke but all of which may be absorbed should the cigarette be ingested.
