Nicotine

September 17, 2011

Nicotine was first identified in the early 1800s. It is a stimulant from the same family as cocaine. Nicotine is a naturally occurring colorless liquid that turns brown when burned and acquires the odor of tobacco when exposed to air. Most nicotine is obtained through tobacco use.

THE EFFECTS OF NICOTINE

Most cigarettes in the U.S. market contain 10 mg or more of nicotine. The effects of nicotine in people are influenced by: (a) the rate and route of dosing, (b) the development of tolerance, and (c) the metabolism of nicotine.

The average smoker smokes about 1packs of cigarettes a day and takes between 10 and 20 puffs per cigarette. According to the National Institute on Drug Abuse, this average smoker gets 300 “hits” of nicotine to the brain each day. The average smoker takes in 1-2 mg of nicotine per cigarette. It takes only a few seconds for nicotine to enter the bloodstream after inhalation and less than 10 s to reach the brain. It is likely that the targets of nicotine in the central nervous system (CNS) are receptors found throughout the brain called nicotinic acetylcholine receptors (nAChRs). Cigar and pipe smokers typically do not inhale the smoke, so nicotine is absorbed more slowly through the mucosal membranes of their mouths.

Unlike most abused drugs, a smoker does not become intoxicated on cigarettes. In fact, the immediate effects of smoking are positive effects on mood, alertness, and ability to concentrate. This is because nicotine is activating the brain circuitry that regulates feelings of pleasure. The acute effects of nicotine dissipate in a few minutes, causing many smokers to continue dosing frequently throughout the day to maintain the drug’s pleasurable effects. These effects are the primary reasons why so many smokers continue to smoke.

Eventually, the body develops a tolerance to nicotine’s effects and physical dependence develops. When someone who is nicotine dependent tries to quit smoking, they experience a nicotine withdrawal syndrome. Symptoms of nicotine withdrawal include irritability, insomnia, anxiety, difficulty concentrating, depressed mood, decreased heart rate, and increased appetite. The withdrawal symptoms may peak within 1-4 days and persist for 3-4 weeks. Their persistence makes cessation difficult; most smokers who try to quit on their own relapse within a few days.

Nicotine has a rapid onset and short duration of action. Nicotine disappears from the body in a few hours. Under natural conditions, persons may have some cigarettes as often as every 20-30 min to keep a steady dose of nicotine in their body. Recent studies are looking at genetic variations in the enzymes that metabolize nicotine. According to Walton and colleagues “it should soon be possible to identify fast metabolizers (of nicotine) by DNA analysis.”

Nicotine has different effects on mood. At first, it acts as an “upper” and, after a while, it acts as a “downer.” Recent studies are examining the relationship between nicotine and depression.

Niaura et al. (2001) review the literature on maternal influences of smoking behaviors on their offspring. In particular, several studies have examined the effects of in utero exposure to smoking and the neuropsychiatric effects on the offspring. In women who smoke, neuropsychiatric deficits may be transmitted from mother to child.

NICOTINE ADDICTION

The addictive power of nicotine is shown in animal studies in which rats will self-administer intravenous nicotine. Despite knowing the negative health consequences, many adult smokers are addicted to nicotine. They crave for the cigarette within 15 min of awakening; they compulsively seek out nicotine throughout the day; and they find it difficult to refrain from smoking in areas where it is prohibited. Recent research studies are examining whether smoking, nicotine dependence, and nicotine addiction runs in families and whether genetic variations in brain neurotransmitter receptors may predispose someone to nicotine addiction.

TREATING NICOTINE ADDICTION

According to the Tobacco Advisory Group of the Royal College of Physicians in London, nicotine addiction is “a life-threatening, but treatable disorder.” In fact, nicotine has been developed as a medication to assist smoking cessation. Nicotine replacement therapy (NRT) is a safe, approved method that helps take care of the nicotine addiction, while the smoker works on breaking the smoking habit. Often, NRT in the form of nicotine patch, gum, or inhalant is combined with some form of behavioral treatment program. Another medication used for nicotine addiction is the Bupropion slow-release (SR). NRT and Bupropion SR are Food and Drug Administration (FDA) approved and are prescribed to alleviate withdrawal symptoms, depressive symptoms, or to delay weight gain following smoking cessation.

SEE ALSO: Cardiovascular disease, Coronary risk factors, Lung disease, Smoking, Tobacco

Suggested Reading

  • Coleman, T., & West, R. (2001). Newly available treatment for nicotine addiction. British Medical Journal, 322, 1076-1077.
  • Manuda, M., Johnstone, E., Murphy, M., & Walton, R. (2001). New directions in the genetic mechanism underlying nicotine addiction. Addiction Biology, 6, 109-117.
  • National Institute on Drug Abuse Report Series: Nicotine addiction. www.nida.gov
  • Niaura, R., Bock, B., Lloyd, E. E., Brown, R., Lipsitt, L. P., & Buka, S. (2001). Maternal transmission of nicotine dependence: Psychiatric, neurocognitive and prenatal factors. American Journal of Addiction, 10, 16—29.
  • Tobacco Advisory Group of the Royal College of Physicians. (2000). Nicotine addiction in Britain. London: Author.
  • Walton, R., Johnstone, E., Nunafo, M., Neville, M., & Griffiths, S. (2001). Genetic clues to the molecular basis of tobacco addiction and progress towards personalized therapy. Trends in Molecular Medicine, 7, 70-76.
  • Watkins, S. S., Koob, G. F., & Markou, A. (2000). Neural mechanisms underlying nicotine addiction: Acute positive reinforcement and withdrawal. Nicotine Tobacco Research, 2, 19-37.

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