Nicotine
Nicotine poisoning may occur in children after they ingest tobacco or drink saliva expectorated by a tobacco chewer (which is often collected in a can or other containers), in children or adults after accidental or suicidal ingestion of nicotine-containing pesticides (eg, Black Leaf 40, which contains 40% nicotine sulfate), and occasionally after cutaneous exposure to nicotine, such as occurs among tobacco harvesters (“green tobacco sickness”). Nicotine chewing gum (Nicorette and generics), transdermal delivery formulations (Habitrol, Nicoderm, Nicotrol, and generics), and nicotine nasal spray, inhalers, and lozenges are widely available as adjunctive therapy for smoking cessation. Nicotine is found in various smokeless tobacco products (snuff and chewing tobacco), including recently marketed compressed dissolvable tobacco tablets that look like candy. Alkaloids similar to nicotine (anabasine, cytisine, coniine, and lobeline) are found in several plant species (see “Plants”). Neonicotinoid insecticides (imidocloprid and others) are widely used both in agriculture and for flea control in dogs and cats.
Mechanism of toxicity
Nicotine binds to nicotinic cholinergic receptors, resulting initially, via actions on autonomic ganglia, in predominantly sympathetic nervous stimulation. With higher doses, parasympathetic stimulation and then ganglionic and neuromuscular blockade may occur. Direct effects on the brain may also result in vomiting and seizures..
Pharmacokinetics. Nicotine is absorbed rapidly by all routes and enters the brain quickly. The apparent volume of distribution is 3 L/kg. It is rapidly metabolized and to a lesser extent excreted in the urine, with a half-life of 120 minutes. Neonicotinoids penetrate the CNS less well than nicotine and therefore are less toxic than nicotine at low levels of exposure.
Toxic dose. Owing to presystemic metabolism and spontaneous vomiting, which limit absorption, the bioavailability of nicotine that is swallowed is about 30–40%. Rapid absorption of 2–5 mg can cause nausea and vomiting, particularly in a person who does not use tobacco habitually. Absorption of 40–60 mg in an adult is said to be lethal, although this dose spread throughout the day is not unusual in a cigarette smoker.
Tobacco.
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