What Is Nicotine?
Nicotine, one of more than 4,000 chemicals found in the smoke from tobacco products such as cigarettes, cigars, and pipes, is the primary component in tobacco that acts on the brain. Smokeless tobacco products such as snuff and chewing tobacco also contain many toxins as well as high levels of nicotine. Nicotine, recognized as one of the most frequently used addictive drugs, is a naturally occurring colorless liquid that turns brown when burned and acquires the odor of tobacco when exposed to air.
Is Nicotine Addictive?
Yes. Most smokers use tobacco regularly because they are addicted to nicotine. Most smokers identify tobacco as harmful and express a desire to reduce or stop using it, and nearly 35 million of them make a serious attempt to quit each year. Unfortunately, less than 7 percent of those who try to quit on their own achieve more than 1 year of abstinence; most relapse within a few days of attempting to quit.
What Is the Extent and Impact of Tobacco Use?
An estimated 56.3 million Americans are current smokers and 7.3 million use smokeless tobacco, which means that nicotine is one of the most widely abused substances. Each day in the United States more than 2,000 people under the age of 18 begin daily smoking. Since 1975, nicotine in the form of cigarettes has consistently been the substance the greatest number of high school students use daily.
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. More 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. 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. High levels of craving for tobacco may persist for 6 months or longer. 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 make asthma symptoms in adults and children worse. 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.
Smoking and Pregnancy: What are the Risks?
In pregnant women, carbon monoxide (a lethal gas) and the high doses of nicotine obtained when they inhale tobacco smoke interferes with oxygen supply to the fetus. Nicotine crosses the placenta Nicotine is concentrated in fetal blood, amniotic fluid, and breast milk. Another ingredient of tobacco smoke, carbon monoxide, has been shown to inhibit the release of oxygen into fetal tissues. These factors, combined, may account for the developmental delays seen in some fetuses and infants of smoking mothers.
Women who smoke during pregnancy are at greater risk than nonsmokers for premature delivery, and there is a risk of lower birth weight for infants carried to term. In the United States it is estimated that 20 percent or more of pregnant women smoke throughout their pregnancies. The adverse effects of smoking may occur in every trimester of pregnancy; they range from spontaneous abortions in the first trimester to increased premature delivery rates and decreased birth weights in the final trimester.
Are There Effective Treatments for Nicotine Addiction?
Yes, extensive research has shown that behavioral and pharmacological treatments such as the nicotine patch and gum, and buproprion (Zyban) for nicotine addiction do work. For those individuals motivated to quit smoking, a combination of behavioral and pharmacological treatments can increase the success rate approximately twofold over placebo treatments. Smoking cessation can have an immediate positive impact on an individual's health; for example, a 35-year-old man who quits smoking will, on the average, increase his life expectancy by 5.1 years.