National Institute on Drug Abuse
Research Report Series

Nicotine Addiction

[Nicotine Addiction Report Index] << What is Nicotine? | Effective Treatments for Nicotine Addiction >>

How does nicotine deliver its effect?

Nicotine can act as both a stimulant and a sedative. Immediately after exposure to nicotine, there is a "kick" caused in part by the drug's stimulation of the adrenal glands and resulting discharge of epinephrine (adrenaline). The rush of adrenaline stimulates the body and causes a sudden release of glucose as well as an increase in blood pressure, respiration, and heart rate. Nicotine also suppresses insulin output from the pancreas, which means that smokers are always slightly hyperglycemic. In addition, nicotine indirectly causes a release of dopamine in the brain regions that control pleasure and motivation. This reaction is similar to that seen with other drugs of abuse - such as cocaine and heroin - and it is thought to underlie the pleasurable sensations experienced by many smokers. In contrast, nicotine can also exert a sedative effect, depending on the level of the smoker's nervous system arousal and the dose of nicotine taken.

What happens when nicotine
is taken for long periods
of time?

Chronic exposure to nicotine results in addiction. Research is just beginning to document all of the neurological changes that accompany the development and maintenance of nicotine addiction. The behavioral consequences of these changes are well documented, however. Greater than 90 percent of those smokers who try to quit without seeking treatment fail, with most relapsing within a week.

Repeated exposure to nicotine results in the development of tolerance, the condition in which higher doses of a drug are required to produce the same initial stimulation. Nicotine is metabolized fairly rapidly, disappearing from the body in a few hours. Therefore some tolerance is lost overnight, and smokers often report that the first cigarettes of the day are the strongest and/or the "best." As the day progresses, acute tolerance develops, and later cigarettes have less effect.

Cessation of nicotine use is followed by a withdrawal syndrome that may last a month or more; it includes symptoms that can quickly drive people back to tobacco use. Nicotine withdrawal symptoms include irritability, craving, cognitive and attentional deficits, sleep disturbances, and increased appetite and may begin within a few hours after the last cigarette. Symptoms peak within the first few days and may subside within a few weeks. For some people, however, symptoms may persist for months or longer.

An important but poorly understood component of the nicotine withdrawal syndrome is craving, an urge for nicotine that has been described as a major obstacle to successful abstinence. High levels of craving for tobacco may persist for 6 months or longer. While the withdrawal syndrome is related to the pharmacological effects of nicotine, many behavioral factors also can affect the severity of withdrawal symptoms. For some people, the feel, smell, and sight of a cigarette and the ritual of obtaining, handling, lighting, and smoking the cigarette are all associated with the pleasurable effects of smoking and can make withdrawal or craving worse. While nicotine gum and patches may alleviate the pharmacological aspects of withdrawal, cravings often persist.

What are the medical
consequences of nicotine use?

The medical consequences of nicotine exposure result from effects of both the nicotine itself and how it is taken. The most deleterious effects of nicotine addiction are the result of tobacco use, which accounts for one-third of all cancers. Foremost among the cancers caused by tobacco is lung cancer - the number one cancer killer of both men and women. Cigarette smoking has been linked to about 90 percent of all lung cancer cases.

In addition to lung cancer, smoking also causes lung diseases such as chronic bronchitis and emphysema, and it has been found to exacerbate asthma symptoms in adults and children. Smoking is also associated with cancers of the mouth, pharynx, larynx, esophagus, stomach, pancreas, cervix, kidney, ureter, and bladder. The overall rates of death from cancer are twice as high among smokers as among nonsmokers, with heavy smokers having rates that are four times greater than those of nonsmokers. Cigarette smoking is the most important preventable cause of cancer in the United States.

In addition to its ability to cause cancer, a relationship between cigarette smoking and coronary heart disease was first reported in the 1940s. Since that time, it has been well documented that smoking substantially increases the risk of heart disease, including stroke, heart attack, vascular disease, and aneurysm. It is estimated that nearly one-fifth of deaths from heart disease are attributable to smoking.

While we often think of medical consequences that result from direct use of tobacco products, passive or secondary smoke also increases the risk for many diseases. Environmental tobacco smoke (ETS) is a major source of indoor air contaminants; secondhand smoke is estimated to cause approximately 3,000 lung cancer deaths per year among nonsmokers and contributes to as many as 40,000 deaths related to cardiovascular disease. Exposure to tobacco smoke in the home increases the severity of asthma for children and is a risk factor for new cases of childhood asthma. ETS exposure has been linked also with sudden infant death syndrome. Additionally, dropped cigarettes are the leading cause of residential fire fatalities, leading to more than 1,000 such deaths each year. At higher doses, such as the nicotine that can be found in some insecticide sprays, nicotine can be extremely toxic, causing vomiting, tremors, convulsions, and death. Nicotine poisoning has been reported from accidental ingestion of insecticides by adults and ingestion of tobacco products by children and pets. Death usually results in a few minutes from respiratory failure caused by paralysis.

Laboratory research indicates that cigarette smoking causes toxic cardiovascular effects. For this reason, nicotine replacement medicines such as nicotine gum and the patch have been extensively evaluated for cardiovascular toxicity, especially for patients with cardiac disease. These trials suggest that use of nicotine replacements for smoking cessation does not increase cardiovascular risk. These findings are consistent with the generally slower and lower doses of nicotine obtained from the medicines as compared to tobacco products, and to the absence of carbon monoxide and numerous other toxins in tobacco smoke.

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