Nicotine is addictive.[11] In lesser doses (an average cigarette yields about 2 mg of absorbed nicotine), the substance acts as a stimulant in mammals, while high amounts (50–100 mg) can be harmful.[12][13][14] This stimulant effect is a contributing factor to the addictive properties of tobacco smoking. Nicotine's addictive nature includes psychoactive effects, drug-reinforced behavior, compulsive use, relapse after abstinence, physical dependence and tolerance.[15]
It is widely held that nicotine, delivered as a drug in regulated nicotine replacement therapy devices at recommended doses, itself poses little health risks, except among certain vulnerable groups.[16] Nicotine is associated with potential birth defects and at high enough-doses, poisonings.[17][18] In vitro studies have associated it with cancer, but carcinogenicity has not been demonstrated in vivo.[18] There is inadequate research to demonstrate that nicotine is associated with cancer in humans.[19] As medicine, nicotine is used to help with quitting smoking and has good safety in this form.[20] During pregnancy, there are risks to child later in life for type 2 diabetes, obesity, hypertension, neurobehavioral defects, respiratory dysfunction, and infertility.[20] At high enough doses, nicotine is lethal.[21] It is unlikely that a person would overdose on nicotine through smoking alone.[22] The use of electronic cigarettes, which are designed to be refilled with nicotine-containing e-liquid, has renewed interest in nicotine overdoses, especially with regard to the possibility of young children ingesting the liquids.[23]
