The LD50 of nicotine is 50 mg/kg for rats and 3 mg/kg for mice 0.5-1.0 mg/kg can be a lethal dosage for adult humans, and 0.1 mg/kg for children. Nicotine therefore has a high toxicity in comparison to many other alkaloids such as cocaine, which in mice has an LD50 of 95.1 mg/kg.
A person can overdose on nicotine through a combination of nicotine patches, nicotine gum, nicotine inhaler cartridges and/or tobacco smoking at the same time. Ingestion of nicotine pharmaceuticals, tobacco products, or nicotine containing plants may also lead to poisoning. Smoking excessive amounts of tobacco has also lead to poisoning; a case was reported where two brothers smoked 17 and 18 pipes of tobacco in succession and were both fatally poisoned.Spilling an extremely high concentration of nicotine onto the skin can result in intoxication or even death since nicotine readily passes into the bloodstream following skin contact.