Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco.[15] Nicotine is also present atppb concentrations in edible plants in the familySolanaceae, includingpotatoes,tomatoes, andeggplants,[16] though sources disagree on whether this has any biological significance to human consumers.[16] It functions as anantiherbivore toxin; consequently, nicotine was widely used as aninsecticide in the past,[17][18] andneonicotinoids (structurally similar to nicotine), such asimidacloprid, are some of the most effective and widely used insecticides.
Nicotine is highlyaddictive.[19][20][21] Slow-release forms (gums and patches, when used correctly) can be less addictive and help in quitting.[22][23][24][25] Animal research suggests thatmonoamine oxidase inhibitors present in tobacco smoke may enhance nicotine's addictive properties.[26][27] An averagecigarette yields about 2 mg of absorbed nicotine.[28]The estimated lower dose limit for fatal outcomes is 500–1,000 mg of ingested nicotine for an adult (6.5–13 mg/kg).[26][28] Nicotine addiction involves drug-reinforced behavior, compulsive use, and relapse following abstinence.[29] Nicotinedependence involvestolerance,sensitization,[30]physical dependence, andpsychological dependence,[31] which can cause distress.[32][33]Nicotine withdrawal symptoms includedepression, stress, anxiety,irritability, difficulty concentrating, and sleep disturbances.[2] Mild nicotine withdrawal symptoms are measurable in unrestricted smokers, who experience normal moods only as their blood nicotine levels peak, with each cigarette.[34] On quitting, withdrawal symptoms worsen sharply, then gradually improve to a normal state.[34]
Nicotine use as a tool forquitting smoking has a good safety history.[35] Animal studies suggest that nicotine may adversely affect cognitive development in adolescence, but the relevance of these findings to human brain development is disputed.[36][26] At low amounts, it has a mildanalgesic effect.[37] According to theInternational Agency for Research on Cancer, "nicotine is not generally considered to be a carcinogen".[38][39]TheSurgeon General of the United States indicates that evidence is inadequate to infer the presence or absence of a causal relationship between exposure to nicotine and risk for cancer.[40] Nicotine has been shown to produce birth defects in humans and is considered ateratogen.[41][42] Themedian lethal dose of nicotine in humans is unknown.[43] High doses are known to causenicotine poisoning, organ failure, and death through paralysis of respiratory muscles,[40][44] though serious or fatal overdoses are rare.[45]
The primarytherapeutic use of nicotine is treating nicotine dependence to eliminatesmoking and the damage it does to health. Controlled levels of nicotine are given to patients throughgums,dermal patches, lozenges, inhalers, or nasal sprays to wean them off their dependence. A 2018Cochrane Collaboration review found high-quality evidence that all current forms of nicotine replacement therapy (gum, patch, lozenges, inhaler, and nasal spray) increase the chances of successfully quitting smoking by50–60%, regardless of setting.[46]
Combiningnicotine patch use with a faster acting nicotine replacement, like gum or spray, improves the odds of treatment success.[47]
In contrast to recreational nicotine products, which have been designed to maximize the likelihood of addiction, nicotine replacement products (NRTs) are designed to minimize addictiveness.[40]: 112 The more quickly a dose of nicotine is delivered and absorbed, the higher the addiction risk.[32]
Nicotine has been used as aninsecticide since at least 1690, in the form of tobacco extracts or as pure nicotine sulphate[18][48][49] (although other components of tobacco also seem to have pesticide effects).[50] It acts on thenicotinic acetylcholine receptor, and gave the receptor its name. Nicotine is inIRAC group 4B. Nicotine insecticides have been banned in the US since 2014,[51] including use on organic crops,[52] and caution is recommended for small gardeners.[53] Nicotine pesticides have been banned in the EU since 2009.[54] Foods are imported from countries in which nicotine pesticides are allowed, such as China, but foods may not exceed maximum nicotine levels.[54][55]Neonicotinoids, such asimidacloprid, which are derived from and structurally similar to nicotine, are widely used as agricultural and veterinary pesticides as of 2016.[56][48]
Nicotine use for tobacco cessation has few contraindications.[68]
It is not known whether nicotine replacement therapy is effective for smoking cessation in adolescents, as of 2014.[69] It is therefore not recommended to adolescents.[70] It is not safe to use nicotine during pregnancy or breastfeeding, although it is safer than smoking. The desirability of NRT use in pregnancy is therefore debated.[71][72][73]
Randomized trials and observational studies of nicotine replacement therapy in cardiovascular patients show no increase in adverse cardiovascular events compared to those treated with placebo.[74] Using nicotine products during cancer treatment may be contraindicated, as nicotine may promote tumour growth, but temporary use of NRTs to quit smoking may be advised forharm reduction.[75]
Nicotine is classified as a poison,[78][79] and it is "extremely hazardous".[80] However, at doses typically used by consumers, it presents little if any hazard to the user.[81][82][83] A 2018Cochrane Collaboration review lists nine main adverse events related to nicotine replacement therapy:headache,dizziness,lightheadedness,nausea,vomiting, gastrointestinal symptoms,insomnia, abnormaldreams, non-ischemicpalpitations and chest pain, skin reactions, oral/nasal reactions, andhiccups.[84] Many of these were also common in the placebo group without nicotine.[84] Palpitations and chest pain were deemed "rare" and there was no evidence of an increased number of serious cardiac problems compared to the placebo group, even in people with established cardiac disease.[46] The common side effects from nicotine exposure are listed in the table below. Serious adverse events due to the use of nicotine replacement therapy are extremely rare.[46] At low amounts, it has a mildanalgesic effect.[37] However, at sufficiently high doses, nicotine may result in nausea, vomiting,diarrhea,salivation,bradycardia, and possiblyseizures,hypoventilation, and death.[85]
Common side effects of nicotine use according to route of administration and dosage form
Nicotine reduces the amount ofrapid eye movement (REM) sleep,slow-wave sleep (SWS), and total sleep time in healthy nonsmokers given nicotine via atransdermal patch, and the reduction isdose-dependent.[89] Acute nicotine intoxication has been found to significantly reduce total sleep time and increase REM latency,sleep onset latency, andnon-rapid eye movement (NREM) stage 2 sleep time.[89][90] Depressive non-smokers experience mood and sleep improvements under nicotine administration; however, subsequent nicotine withdrawal has a negative effect on both mood and sleep.[91]
Nicotine exerts several significant effects on thecardiovascular system. Primarily, it stimulates thesympathetic nervous system, leading to the release ofcatecholamines. This activation results in an increase inheart rate andblood pressure, as well as enhancedmyocardial contractility, which raises the workload on the heart. Additionally, nicotine causes systemicvasoconstriction, including constriction of coronary arteries, which can reduce blood flow to the heart. Long-term exposure to nicotine may impairendothelial function, potentially contributing toatherosclerosis. Furthermore, nicotine has been associated with the development ofcardiac arrhythmias, particularly in individuals who already have underlying heart disease.[92]
The effects of nicotine can be differentiated between short-term and long-term use. Short-term nicotine use, such as that associated withnicotine replacement therapy (NRT) for smoking cessation, appears to pose little cardiovascular risk, even for patients with known cardiovascular conditions. In contrast, longer-term nicotine use may not accelerate atherosclerosis but could contribute to acute cardiovascular events in those with pre-existing cardiovascular disease. Many severe cardiovascular effects traditionally associated with smoking may not be solely attributable to nicotine itself. Cigarette smoke contains numerous other potentially cardiotoxic substances, includingcarbon monoxide and oxidant gases.[92]
A 2016 review of the cardiovascular toxicity of nicotine concluded, "Based on current knowledge, we believe that the cardiovascular risks of nicotine from e-cigarette use in people without cardiovascular disease are quite low. We have concerns that nicotine from e-cigarettes could pose some risk for users with cardiovascular disease."[92]
A 2018Cochrane review found that, in rare cases, nicotine replacement therapy can cause non-ischemic chest pain (i.e., chest pain that is unrelated to aheart attack) andheart palpitations, but does not increase the incidence of serious cardiac adverse events (i.e., myocardial infarction,stroke, andcardiac death) relative to controls.[46]
In the short term, nicotine causes a transient increase inblood pressure. Long term, epidemiological studies generally show increased blood pressure andhypertension among nicotine users.[92]
Top: this depicts the initial effects of high dose exposure to an addictive drug ongene expression in thenucleus accumbens for various Fos family proteins (i.e.,c-Fos,FosB,ΔFosB,Fra1, andFra2). Bottom: this illustrates the progressive increase in ΔFosB expression in the nucleus accumbens following repeated twice daily drug binges, where thesephosphorylated (35–37 kilodalton) ΔFosBisoforms persist in theD1-typemedium spiny neurons of the nucleus accumbens for up to 2 months.[93][94]
Nicotine is highlyaddictive but paradoxically has quite weak reinforcing property compared to other drugs of abuse in various animals.[20][21][95][96] Its addictiveness depends on how it is administered and also depends upon form in which nicotine is used.[24] Animal research suggests thatmonoamine oxidase inhibitors,acetaldehyde[96][97] and other constituents in tobacco smoke may enhance its addictiveness.[26][27]Nicotine dependence involves aspects of bothpsychological dependence andphysical dependence, since discontinuation of extended use has been shown to produce bothaffective (e.g., anxiety, irritability, craving,anhedonia) andsomatic (mild motor dysfunctions such astremor) withdrawal symptoms.[2] Withdrawal symptoms peak in one to three days[98] and can persist for several weeks.[99] Even though other drugs of dependence can have withdrawal states lasting 6 months or longer, this does not appear to occur with cigarette withdrawal.[100]
Normal between-cigarettes discontinuation, in unrestricted smokers, causes mild but measurable nicotine withdrawal symptoms.[34] These include mildly worse mood, stress, anxiety, cognition, and sleep, all of which briefly return to normal with the next cigarette.[34] Smokers have a worse mood than they typically would have if they were not nicotine-dependent; they experience normal moods only immediately after smoking.[34] Nicotine dependence is associated with poor sleep quality and shorter sleep duration among smokers.[101][102]
In dependent smokers, withdrawal causes impairments in memory and attention, and smoking during withdrawal returns these cognitive abilities to pre-withdrawal levels.[103] The temporarily increased cognitive levels of smokers after inhaling smoke are offset by periods of cognitive decline during nicotine withdrawal.[34] Therefore, the overall daily cognitive levels of smokers and non-smokers are roughly similar.[34]
Nicotine activates themesolimbic pathway andinduces long-termΔFosB expression (i.e., producesphosphorylated ΔFosBisoforms) in thenucleus accumbens when inhaled or injected frequently or at high doses, but not necessarily when ingested.[104][105][106] Consequently, high daily exposure (possibly excludingoral route) to nicotine can cause ΔFosB overexpression in the nucleus accumbens, resulting in nicotine addiction.[104][105]
Contrary topopular belief, nicotine itself does not cause cancer in humans,[39][107] although it is unclear whether it functions as atumor promoter as of 2012[update].[108] A 2018 report by the USNational Academies of Sciences, Engineering, and Medicine concludes, "[w]hile it is biologically plausible that nicotine can act as a tumor promoter, the existing body of evidence indicates this is unlikely to translate into increased risk of human cancer."[109]
Nicotine promotes lung cancer development by enhancing proliferation, angiogenesis, migration, invasion, and epithelial–mesenchymal transition (EMT) via nAChRs, which are present in lung cancer cells.[111] Additionally, nicotine-induced EMT contributes to drug resistance in cancer cells.[112]
Nicotine in tobacco can form carcinogenictobacco-specific nitrosamines through anitrosation reaction. This occurs mostly in the curing and processing of tobacco. However, nicotine in the mouth and stomach can react to formN-nitrosonornicotine,[113] a known type 1 carcinogen,[114] suggesting that consumption of non-tobacco forms of nicotine may still play a role in carcinogenesis.[115]
Nicotine has been shown to produce birth defects in some animal species, but not others;[42] consequently, it is considered to be a possibleteratogen in humans.[42] Inanimal studies that resulted in birth defects, researchers found that nicotine negatively affects fetalbrain development and pregnancy outcomes;[42][40] the negative effects on early brain development are associated with abnormalities inbrain metabolism andneurotransmitter system function.[119] Nicotine crosses theplacenta and is found in the breast milk of mothers who smoke as well as mothers who inhalepassive smoke.[120]
Nicotine exposurein utero is responsible for several complications of pregnancy and birth: pregnant women who smoke are at greater risk for bothmiscarriage andstillbirth and infants exposed to nicotinein utero tend to have lowerbirth weights.[121] AMcMaster University research group observed in 2010 that rats exposed to nicotine in the womb (via parenteral infusion) later in life had conditions includingtype 2 diabetes,obesity,hypertension, neurobehavioral defects, respiratory dysfunction, andinfertility.[122]
It is unlikely that a person would overdose on nicotine through smoking alone. The USFood and Drug Administration (FDA) stated in 2013 that there are no significant safety concerns associated with the use of more than one form ofover-the-counter (OTC)nicotine replacement therapy at the same time, or using OTC NRT at the same time as another nicotine-containing product, like cigarettes.[123] Themedian lethal dose of nicotine in humans is unknown.[43][28] Nevertheless, nicotine has a relatively hightoxicity in comparison to many other alkaloids such ascaffeine, which has an LD50 of 127 mg/kg when administered to mice.[124] At sufficiently high doses, it is associated with nicotine poisoning,[40] which, while common in children (in whom poisonous and lethal levels occur at lower doses per kilogram of body weight[37]) rarely results in significant morbidity or death.[42] The estimated lower dose limit for fatal outcomes is 500–1,000 mg of ingested nicotine for an adult (6.5–13 mg/kg).[26][28]
The initial symptoms of a nicotine overdose typically includenausea, vomiting, diarrhea,hypersalivation, abdominal pain,tachycardia (rapid heart rate),hypertension (high blood pressure),tachypnea (rapid breathing), headache, dizziness,pallor (pale skin), auditory or visual disturbances, and perspiration, followed shortly after by markedbradycardia (slow heart rate),bradypnea (slow breathing), andhypotension (low blood pressure).[42] An increased respiratory rate (i.e.,tachypnea) is one of the primarysigns of nicotine poisoning.[42] At sufficiently high doses,somnolence (sleepiness or drowsiness),confusion,syncope (loss of consciousness from fainting),shortness of breath, markedweakness,seizures, andcoma may occur.[7][42] Lethal nicotine poisoning rapidly produces seizures, and death – which may occur within minutes – is believed to be due torespiratory paralysis.[42]
Today nicotine is less commonly used in agriculturalinsecticides, which was a main source of poisoning. More recent cases of poisoning typically appear to be in the form ofGreen Tobacco Sickness (GTS),[42] accidental ingestion oftobacco ortobacco products, or ingestion of nicotine-containing plants.[125][126][127] People who harvest or cultivate tobacco may experience GTS, a type of nicotine poisoning caused by dermal exposure to wet tobacco leaves. This occurs most commonly in young, inexperienced tobacco harvesters who do not consume tobacco.[125][128] People can be exposed to nicotine in the workplace by breathing it in, skin absorption, swallowing it, or eye contact. TheOccupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for nicotine exposure in the workplace as 0.5 mg/m3 skin exposure over an 8-hour workday. The USNational Institute for Occupational Safety and Health (NIOSH) has set arecommended exposure limit (REL) of 0.5 mg/m3 skin exposure over an 8-hour workday. At environmental levels of 5 mg/m3, nicotine isimmediately dangerous to life and health.[129]
By binding tonicotinic acetylcholine receptors in the brain, nicotine elicits its psychoactive effects and increases the levels of severalneurotransmitters in various brain structures – acting as a sort of "volume control".[130][131] Nicotine has a higher affinity for nicotinic receptors in the brain than those inskeletal muscle, though at toxic doses it can induce contractions and respiratory paralysis.[132] Nicotine's selectivity is thought to be due to a particular amino acid difference on these receptor subtypes.[133] Nicotine is unusual in comparison to most drugs, as its profile changes fromstimulant tosedative with increasingdosages, a phenomenon known as "Nesbitt's paradox" after the doctor who first described it in 1969.[134][135] At very high doses it dampensneuronal activity.[136] Nicotine induces both behavioral stimulation and anxiety in animals.[7] Research into nicotine's most predominant metabolite,cotinine, suggests that some of nicotine's psychoactive effects are mediated by cotinine.[137]
Nicotine also activates thesympathetic nervous system,[143] acting viasplanchnic nerves to the adrenal medulla, stimulating the release of epinephrine. Acetylcholine released by preganglionic sympathetic fibers of these nerves acts on nicotinic acetylcholine receptors, causing the release of epinephrine (and norepinephrine) into thebloodstream.
The amount of nicotine absorbed by the body from smoking can depend on many factors, including the types of tobacco, whether the smoke is inhaled, and whether a filter is used. However, it has been found that the nicotine yield of individual products has only a small effect (4.4%) on the blood concentration of nicotine,[149] suggesting "the assumed health advantage of switching to lower-tar and lower-nicotine cigarettes may be largely offset by the tendency of smokers to compensate by increasing inhalation".
Nicotine has a half-life of 1–2 hours.Cotinine is an active metabolite of nicotine that remains in the blood with a half-life of 18–20 hours, making it easier to analyze.[150]
Nicotine ismetabolized in theliver bycytochrome P450 enzymes (mostlyCYP2A6, and also byCYP2B6) andFMO3, which selectively metabolizes (S)-nicotine. A major metabolite iscotinine. Other primary metabolites include nicotineN-oxide,nornicotine, nicotine isomethonium ion, 2-hydroxynicotine and nicotine glucuronide.[151] Under some conditions, other substances may be formed such asmyosmine.[152][153]
Nicotine decreases hunger and as a consequence food consumption, alongside increasingenergy expenditure.[155][156] The majority of research shows that nicotine reduces body weight, but some researchers have found that nicotine may result in weight gain under specific types of eating habits in animal models.[156] Nicotine effect on weight appears to result from nicotine's stimulation of α3β4 nAChR receptors located in thePOMC neurons in the arcuate nucleus and subsequently themelanocortin system, especially the melanocortin-4 receptors on second-order neurons in the paraventricular nucleus of the hypothalamus, thus modulating feeding inhibition.[140][156] POMC neurons are a precursor of the melanocortin system, a critical regulator of body weight and peripheral tissue such as skin and hair.[156]
Nicotine is ahygroscopic, colorless[80] to yellow-brown, oily liquid, that is readily soluble in alcohol, ether or light petroleum. It ismiscible withwater in its neutral aminebase form between 60 °C and 210 °C. It is a dibasicnitrogenous base, having Kb1=1×10−6, Kb2=1×10−11.[158] It readily forms ammoniumsalts withacids that are usually solid and water-soluble. Itsflash point is 95 °C and its auto-ignition temperature is 244 °C.[159] Nicotine is readily volatile (vapor pressure 5.5 Pa at 25 °C)[158] On exposure to ultraviolet light or various oxidizing agents, nicotine is converted to nicotine oxide,nicotinic acid (niacin, a B3 vitamer), andmethylamine.[160]
Nicotine ischiral and henceoptically active, having twoenantiomeric forms. The naturally occurring form of nicotine islevorotatory with aspecific rotation of [α]D=–166.4° ((−)-nicotine). Thedextrorotatory form, (+)-nicotine is physiologically less active than (−)-nicotine. (−)-nicotine is more toxic than (+)-nicotine.[161] The salts of (−)-nicotine are usually dextrorotatory; this conversion between levorotatory and dextrorotatory upon protonation is common among alkaloids.[160] The hydrochloride and sulfate salts become optically inactive if heated in a closed vessel above 180 °C.[160]Anabasine is astructural isomer of nicotine, as both compounds have themolecular formulaC10H14N2.
Nicotine that is found in natural tobacco is primarily (99%) the S-enantiomer.[162] Conversely, the most common chemistry synthetic methods for generating nicotine yields a product that is approximately equal proportions of the S- and R-enantiomers.[163] This suggests that tobacco-derived and synthetic nicotine can be determined by measuring the ratio of the two different enantiomers, although means exist for adjusting the relative levels of the enantiomers or performing a synthesis that only leads to the S-enantiomer. There is limited data on the relative physiological effects of these two enantiomers, especially in people. However, the studies to date indicate that (S)-nicotine is more potent than (R)-nicotine and (S)-nicotine causes stronger sensations or irritation than (R)-nicotine. Studies have not been adequate to determine the relative addictiveness of the two enantiomers in people.
Structure of protonated nicotine (left) and structure of the counterion benzoate (right). This combination is used in some vaping products to increase nicotine delivery to the lung.
The first laboratory preparation of nicotine (as itsracemate) was described in 1904.[165]The starting material was an N-substitutedpyrrole derivative, which was heated to convert it by a[1,5] sigmatropic shift to theisomer with a carbon bond between the pyrrole and pyridine rings, followed bymethylation and selective reduction of the pyrrole ring using tin and hydrochloric acid.[165][166] Many other syntheses of nicotine, in both racemic and chiral forms have since been published.[167]
The biosynthetic pathway of nicotine involves a coupling reaction between the two cyclic structures that comprise nicotine. Metabolic studies show that thepyridine ring of nicotine is derived fromnicotinic acid thepyrrolidine is derived fromN-methyl-Δ1-pyrrollidium cation.[168][169] Biosynthesis of the two component structures proceeds via two independent syntheses, the NAD pathway for nicotinic acid and the tropane pathway forN-methyl-Δ1-pyrrollidium cation.
The NAD pathway in the genusNicotiana begins with the oxidation of aspartic acid into α-amino succinate by aspartate oxidase (AO). This is followed by a condensation withglyceraldehyde-3-phosphate and a cyclization catalyzed by quinolinate synthase (QS) to givequinolinic acid. Quinolinic acid then reacts with phosphoribosyl pyrophosphate catalyzed by quinolinic acid phosphoribosyl transferase (QPT) to form nicotinic acid mononucleotide (NaMN). The reaction now proceeds via the NAD salvage cycle to produce nicotinic acid via the conversion ofnicotinamide by the enzymenicotinamidase.[citation needed]
TheN-methyl-Δ1-pyrrollidium cation used in the synthesis of nicotine is an intermediate in the synthesis of tropane-derived alkaloids. Biosynthesis begins withdecarboxylation ofornithine byornithine decarboxylase (ODC) to produceputrescine. Putrescine is then converted intoN-methyl putrescine viamethylation by SAM catalyzed byputrescineN-methyltransferase (PMT).N-methyl putrescine then undergoesdeamination into 4-methylaminobutanal by theN-methyl putrescine oxidase (MPO) enzyme, 4-methylaminobutanal then spontaneously cyclize intoN-methyl-Δ1-pyrrollidium cation.[citation needed]
The final step in the synthesis of nicotine is the coupling betweenN-methyl-Δ1-pyrrollidium cation and nicotinic acid. Although studies conclude some form of coupling between the two component structures, the definite process and mechanism remains undetermined. The current agreed theory involves the conversion of nicotinic acid into 2,5-dihydropyridine through 3,6-dihydronicotinic acid. The 2,5-dihydropyridine intermediate would then react withN-methyl-Δ1-pyrrollidium cation to formenantiomerically pure (−)-nicotine.[170]
Nicotine can be quantified in blood, plasma, or urine to confirm a diagnosis of poisoning or to facilitate a medicolegal death investigation. Urinary or salivary cotinine concentrations are frequently measured for the purposes of pre-employment and health insurance medical screening programs. Careful interpretation of results is important, since passive exposure to cigarette smoke can result in significant accumulation of nicotine, followed by the appearance of its metabolites in various body fluids.[171][172] Nicotine use is not regulated in competitive sports programs.[173]
Methods for measuring the two enantiomers are straightforward and include normal-phase liquid chromatography,[162] liquid chromatography with a chiral column.[174] However, since methods can be used to alter the two enantiomers, it may not be possible to distinguish tobacco-derived from synthetic nicotine simply by measuring the levels of the two enantiomers. A new approach uses hydrogen and deuterium nuclear magnetic resonance to distinguish tobacco-derived and synthetic nicotine based on differences the substrates used in the natural synthetic pathway performed in the tobacco plant and the substrates most used in synthesis.[175] Another approach measures the carbon-14 content which also differs between natural and laboratory-based tobacco.[176] These methods remain to be fully evaluated and validated using a wide range of samples.
Nicotine is asecondary metabolite produced in a variety of plants in the familySolanaceae, most notably in tobaccoNicotiana tabacum, where it can be found at high concentrations of 0.5 to 7.5%.[183] Nicotine is also found in the leaves of other tobacco species, such asNicotiana rustica (in amounts of 2–14%). Nicotine production is strongly induced in response to wounding as part of ajasmonate-dependent reaction.[184] Specialist insects on tobacco, such as the tobacco hornworm (Manduca sexta), have a number of adaptations to the detoxification and even adaptive re-purposing of nicotine.[185] Nicotine is also found at low concentrations in the nectar of tobacco plants, where it may promoteoutcrossing by affecting the behavior of hummingbird pollinators.[186]
Nicotine occurs in smaller amounts (varying from 2–7 μg/kg, or 20–70 millionths of a percent wet weight[16]) in otherSolanaceaeous plants, including some crop species such aspotatoes,tomatoes,eggplant, andpeppers,[16][187] as well as non-crop species such asDuboisia hopwoodii.[158] The amounts of nicotine in tomatoes lowers substantially as the fruit ripens.[16] A 1999 report found "In some papers it is suggested that the contribution of dietary nicotine intake is significant when compared with exposure to ETS [environmental tobacco smoke] or by active smoking of small numbers of cigarettes. Others consider the dietary intake to be negligible unless inordinately large amounts of specific vegetables are consumed."[16] The amount of nicotine eaten per day is roughly around 1.4 and 2.25 μg/day at the 95th percentile.[16] These numbers may be low due to insufficient food intake data.[16] The concentrations of nicotine in vegetables are difficult to measure accurately, since they are very low (parts per billion range).[188] Pure nicotine tastes "terrible".[80]
Nicotine is named after the tobacco plantNicotiana tabacum, which in turn is named after theFrench ambassador inPortugal,Jean Nicot de Villemain, who sent tobacco and seeds toParis in 1560, presented to the French King,[196] and who promoted their medicinal use. Smoking was believed to protect against illness, particularly the plague.[196]
Tobacco was introduced toEurope in 1559, and by the late 17th century, it was used not only forsmoking but also as aninsecticide. AfterWorld War II, over 2,500 tons of nicotine insecticide were used worldwide, but by the 1980s the use of nicotine insecticide had declined below 200 tons. This was due to the availability of other insecticides that are cheaper and less harmful tomammals.[18]
The nicotine content of popular American-brand cigarettes has increased over time, and one study found that there was an average increase of 1.78% per year between the years of 1998 and 2005.[197]
Although methods of production of synthetic nicotine have existed for decades,[198] it was believed that the cost of making nicotine by laboratory synthesis was cost prohibitive compared to extracting nicotine from tobacco.[199] However, recently synthetic nicotine started to be found in different brands of e-cigarettes and oral pouches and marketed as "tobacco-free."[200]
The US FDA is tasked with reviewing tobacco products such as e-cigarettes and determining which can be authorized for sale. In response to the likelihood that FDA would not authorize many e-cigarettes to be marketed, e-cigarette companies began marketing products that they claimed to contain nicotine that were not made or derived from tobacco, but contained synthetic nicotine instead, and thus, would be outside FDA's tobacco regulatory authority.[201] Similarly, nicotine pouches that claimed to contain non-tobacco (synthetic) nicotine were also introduced. The cost of synthetic nicotine has decreased as the market for the product increased. In March 2022, the U.S. Congress passed a law (theConsolidated Appropriations Act, 2022) that expanded FDA's tobacco regulatory authority to include tobacco products containing nicotine from any source, thereby including products made with synthetic nicotine.
In the United States, nicotine products andnicotine replacement therapy products like Nicotrol are only available to people 18 and above; proof of age is required; not for sale in vending machine or from any source where proof of age cannot be verified. As of 2019, the minimum age to purchase tobacco in the US is 21 at the federal level.[202]
In the European Union, the minimum age to purchase nicotine products is 18. However, there is no minimum age requirement to use tobacco or nicotine products.[203]
In the United Kingdom, the Tobacco and Related Products Regulations 2016 implemented the European directive 2014/40/EU, amended by Tobacco Products and Nicotine Inhaling Products (Amendment etc.) (EU Exit) Regulations 2019 and the Tobacco Products and Nicotine Inhaling Products (Amendment) (EU Exit) Regulations 2020. Additionally other regulations limit advertising, sale and display of tobacco products and other products containing nicotine for human consumption. The Sunak government proposed banning disposable vapes to limit their appeal and affordability for children and to reduce the amount of waste generated.
In someanti-smoking literature, the harm that tobacco smoking and nicotine addiction does is personified asNick O'Teen, represented as a humanoid with some aspect of a cigarette or cigarette butt about him or his clothes and hat.[204] Nick O'Teen was a villain that was created for theHealth Education Council. The character was featured in three animated anti-smokingpublic service announcements in which he tries to get kids addicted to cigarettes before being foiled by theDC Comics characterSuperman.[204]
Nicotine was often compared to caffeine in advertisements in the 1980s by the tobacco industry, and later in the 2010s by the electronic cigarettes industry, in an effort to reduce the stigmatization and the public perception of the risks associated with nicotine use.[205]
While acute/initial nicotine intake causes activation of neuronal nicotinic receptors, chronic low doses of nicotine use leads to desensitization of those receptors (due to the development of tolerance) and results in an antidepressant effect, with early research showing low dose nicotine patches could be an effective treatment ofmajor depressive disorder in non-smokers.[206]
Though tobacco smoking is associated with an increased risk ofAlzheimer's disease,[207] there is evidence that nicotine itself has the potential to prevent and treat Alzheimer's disease.[208]
Smoking is associated with a decreased risk ofParkinson's disease; however, it is unknown whether this is due to people with healthier brain dopaminergic reward centers (the area of the brain affected by Parkinson's) being more likely to enjoy smoking and thus pick up the habit, nicotine directly acting as aneuroprotective agent, or other compounds in cigarette smoke acting as neuroprotective agents.[209]
Nicotine may partly attenuatesensory gating and attentional deficits associated withschizophrenia. Short-term use oftransdermal nicotine was found to improve subjects’ reaction time andalertness in given tasks. Nicotine was not found to improvenegative,positive, or other cognitive symptoms of schizophrenia.[210]
Aphotoactivatable form of nicotine, which releases nicotine when exposed toultraviolet light with certain conditions, has been developed for studying nicotinic acetylcholine receptors in brain tissue.[212]
Severalin vitro studies have investigated the potential effects of nicotine on a range of oral cells. A recent systematic review concluded that nicotine was unlikely to be cytotoxic to oral cellsin vitro in most physiological conditions but further research is needed.[213] Understanding the potential role of nicotine in oral health has become increasingly important given the recent introduction of novel nicotine products and their potential role in helping smokers quit.[214]
^abcD'Souza MS, Markou A (July 2011)."Neuronal mechanisms underlying development of nicotine dependence: implications for novel smoking-cessation treatments".Addiction Science & Clinical Practice.6 (1):4–16.PMC3188825.PMID22003417.Withdrawal symptoms upon cessation of nicotine intake: Chronic nicotine use induces neuroadaptations in the brain's reward system that result in the development of nicotine dependence. Thus, nicotine-dependent smokers must continue nicotine intake to avoid distressing somatic and affective withdrawal symptoms. Newly abstinent smokers experience symptoms such as depressed mood, anxiety, irritability, difficulty concentrating, craving, bradycardia, insomnia, gastrointestinal discomfort, and weight gain (Shiffman and Jarvik, 1976; Hughes et al., 1991). Experimental animals, such as rats and mice, exhibit a nicotine withdrawal syndrome that, like the human syndrome, includes both somatic signs and a negative affective state (Watkins et al., 2000; Malin et al., 2006). The somatic signs of nicotine withdrawal include rearing, jumping, shakes, abdominal constrictions, chewing, scratching, and facial tremors. The negative affective state of nicotine withdrawal is characterized by decreased responsiveness to previously rewarding stimuli, a state called anhedonia.
^abNicotine. PubChem Compound Database. United States National Library of Medicine – National Center for Biotechnology Information. 16 February 2019. Retrieved2 May 2025.
^abcdLandoni JH."Nicotine (PIM)".INCHEM. International Programme on Chemical Safety. Retrieved29 January 2019.
^"Nicotine: Clinical data".IUPHAR/BPS Guide to Pharmacology. International Union of Basic and Clinical Pharmacology.Used as an aid to smoking cessation and for the relief of nicotine withdrawal symptoms.
^abMalenka RC, Nestler EJ, Hyman SE (2009). "Chapter 9: Autonomic Nervous System". In Sydor A, Brown RY (eds.).Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. p. 234.ISBN978-0-07-148127-4.Nicotine ... is a natural alkaloid of the tobacco plant. Lobeline is a natural alkaloid of Indian tobacco. Both drugs are agonists are nicotinic cholinergic receptors ...
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^abcdefghijHartmann-Boyce J, Chepkin SC, Ye W, Bullen C, Lancaster T (May 2018)."Nicotine replacement therapy versus control for smoking cessation".The Cochrane Database of Systematic Reviews.5 (5): CD000146.doi:10.1002/14651858.CD000146.pub5.PMC6353172.PMID29852054.There is high-quality evidence that all of the licensed forms of NRT (gum, transdermal patch, nasal spray, inhalator and sublingual tablets/lozenges) can help people who make a quit attempt to increase their chances of successfully stopping smoking. NRTs increase the rate of quitting by 50% to 60%, regardless of setting, and further research is very unlikely to change our confidence in the estimate of the effect. The relative effectiveness of NRT appears to be largely independent of the intensity of additional support provided to the individual. A meta-analysis of adverse events associated with NRT included 92 RCTs and 28 observational studies, and addressed a possible excess of chest pains and heart palpitations among users of NRT compared with placebo groups (Mills 2010). The authors report an OR of 2.06 (95% CI 1.51 to 2.82) across 12 studies. We replicated this data collection exercise and analysis where data were available (included and excluded) in this review, and detected a similar but slightly lower estimate, OR 1.88 (95% CI 1.37 to 2.57; 15 studies; 11,074 participants; OR rather than RR calculated for comparison; Analysis 6.1). Chest pains and heart palpitations were an extremely rare event, occurring at a rate of 2.5% in the NRT groups compared with 1.4% in the control groups in the 15 trials in which they were reported at all. A recent network meta-analysis of cardiovascular events associated with smoking cessation pharmacotherapies (Mills 2014), including 21 RCTs comparing NRT with placebo, found statistically significant evidence that the rate of cardiovascular events with NRT was higher (RR 2.29 95% CI 1.39 to 3.82). However, when only serious adverse cardiac events (myocardial infarction, stroke and cardiovascular death) were considered, the finding was not statistically significant (RR 1.95 95% CI 0.26 to 4.30).
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^"Nicotine: Biological activity".IUPHAR/BPS Guide to Pharmacology. International Union of Basic and Clinical Pharmacology. Retrieved7 February 2016.Kis as follows; α2β4=9900nM [5], α3β2=14nM [1], α3β4=187nM [1], α4β2=1nM [4,6]. Due to the heterogeneity of nACh channels we have not tagged a primary drug target for nicotine, although the α4β2 is reported to be the predominant high affinity subtype in the brain which mediates nicotine addiction
^abStolerman IP, Jarvis MJ (January 1995). "The scientific case that nicotine is addictive".Psychopharmacology.117 (1):2–10, discussion 14–20.doi:10.1007/BF02245088.PMID7724697.S2CID8731555.
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^Bruin JE, Gerstein HC, Holloway AC (August 2010)."Long-term consequences of fetal and neonatal nicotine exposure: a critical review".Toxicological Sciences.116 (2):364–74.doi:10.1093/toxsci/kfq103.PMC2905398.PMID20363831.there is no safe dose of nicotine during pregnancy... The general consensus among clinicians is that more information is needed about the risks of NRT use during pregnancy before well-informed definitive recommendations can be made to pregnant women... Overall, the evidence provided in this review overwhelmingly indicates that nicotine should no longer be considered thesafe component of cigarette smoke. In fact, many of the adverse postnatal health outcomes associated with maternal smoking during pregnancy may be attributable, at least in part, to nicotine alone.
^Royal College of Physicians."Nicotine Without Smoke -- Tobacco Harm Reduction". p. 125. Retrieved30 September 2020.Use of nicotine alone, in the doses used by smokers, represents little if any hazard to the user.
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^Nestler EJ (December 2012)."Transcriptional mechanisms of drug addiction".Clinical Psychopharmacology and Neuroscience.10 (3):136–143.doi:10.9758/cpn.2012.10.3.136.PMC3569166.PMID23430970.The 35–37 kD ΔFosB isoforms accumulate with chronic drug exposure due to their extraordinarily long half-lives. ... As a result of its stability, the ΔFosB protein persists in neurons for at least several weeks after cessation of drug exposure. ... ΔFosB overexpression in nucleus accumbens induces NFκB
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^Bruijnzeel AW (May 2012)."Tobacco addiction and the dysregulation of brain stress systems".Neuroscience and Biobehavioral Reviews.36 (5):1418–41.doi:10.1016/j.neubiorev.2012.02.015.PMC3340450.PMID22405889.Discontinuation of smoking leads to negative affective symptoms such as depressed mood, increased anxiety, and impaired memory and attention...Smoking cessation leads to a relatively mild somatic withdrawal syndrome and a severe affective withdrawal syndrome that is characterized by a decrease in positive affect, an increase in negative affect, craving for tobacco, irritability, anxiety, difficulty concentrating, hyperphagia, restlessness, and a disruption of sleep. Smoking during the acute withdrawal phase reduces craving for cigarettes and returns cognitive abilities to pre-smoking cessation level
^abRuffle JK (November 2014). "Molecular neurobiology of addiction: what's all the (Δ)FosB about?".The American Journal of Drug and Alcohol Abuse.40 (6):428–37.doi:10.3109/00952990.2014.933840.PMID25083822.S2CID19157711.The knowledge of ΔFosB induction in chronic drug exposure provides a novel method for the evaluation of substance addiction profiles (i.e. how addictive they are). Xiong et al. used this premise to evaluate the potential addictive profile of propofol (119). Propofol is a general anaesthetic, however its abuse for recreational purpose has been documented (120). Using control drugs implicated in both ΔFosB induction and addiction (ethanol and nicotine), ...
Conclusions ΔFosB is an essential transcription factor implicated in the molecular and behavioral pathways of addiction following repeated drug exposure. The formation of ΔFosB in multiple brain regions, and the molecular pathway leading to the formation of AP-1 complexes is well understood. The establishment of a functional purpose for ΔFosB has allowed further determination as to some of the key aspects of its molecular cascades, involving effectors such as GluR2 (87,88), Cdk5 (93) and NFkB (100). Moreover, many of these molecular changes identified are now directly linked to the structural, physiological and behavioral changes observed following chronic drug exposure (60,95,97,102). New frontiers of research investigating the molecular roles of ΔFosB have been opened by epigenetic studies, and recent advances have illustrated the role of ΔFosB acting on DNA and histones, truly as amolecular switch (34). As a consequence of our improved understanding of ΔFosB in addiction, it is possible to evaluate the addictive potential of current medications (119), as well as use it as a biomarker for assessing the efficacy of therapeutic interventions (121,122,124).
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