Seventy percent of adult smokers want to quit, and many have made countless attempts, only to be frustrated by repeated failures to remain smoke-free over the long term. The highly addictive nature of nicotine is augmented by the strong habitual association between smoking and daily routines. The combination of physiological addiction and psychological dependence aggravated by ready availability creates a potent synergy. Pharmacotherapy for smoking cessation has provided a critical lifeline, increasing both long- and short-term success in transitioning to a smoke-free lifestyle.

The tobacco plant, Nicotiana tabacum, has been cultivated in the Americas for thousands of years and was exported to Europe almost immediately upon its discovery in the so-called New World. The pleasurable effects of tobacco chewing or smoking are attributable to nicotine (C10H14N2), a naturally occurring alkaloid. Nicotine also represents the addictive component of tobacco. Each cigarette contains 8 to 20 mg of nicotine, but only about 1 to 3 mg are actually absorbed into the body. Experience has shown that so-called “light” cigarettes, with lower measured tar and nicotine levels, are by no means safer, and smokers typically alter subtleties of their inhalation patterns to obtain and maintain nicotine levels comparable to those of standard cigarettes.

Once inhaled, nicotine enters the bloodstream, and the effects are evident in as little as 10 to 15 seconds. It has a half-life of approximately 60 minutes, and is primarily broken down by liver enzymes and excreted in the urine as cotinine. Cotinine has a 24-hour half-life, and its presence is frequently used for screening purposes, including the screening of nonsmoking children of parents who smoke. Pharmacotherapy for smoking cessation addresses the addictive nature of nicotine either by providing direct nicotine replacement in a much less unhealthy form than cigarettes and chew, or by placating the effects of nicotine with an alternative, nonaddictive substitute.

How Nicotine Works
Nicotine users often report that smoking invigorates them, while simultaneously reporting that it has a relaxing effect. The biphasic effect of the drug is not unusual. Alcohol, for example, can have similar effects depending on the amount consumed. The initial physiological action causes a release of adrenaline, stimulating the familiar “fight or flight” response and a corresponding increase in blood pressure, heart rate, and rapid shallow breathing, as the body prepares to escape from danger or defend itself.

Nicotine stimulates the release of acetylcholine, while also mimicking its action. Like acetylcholine, nicotine affects the nervous system by stimulating activity at the synapse where communication takes place between neurons, and creating a burst of activity. Unlike acetylcholine, nicotine activates cholinergic neurons in many regions of the brain simultaneously. This promotes the release of dopamine, an important neurotransmitter in the reward pathways of the brain. It also stimulates the brain to produce more endorphins. Nicotine stimulates the norepinephrine and serotonin systems, enhancing concentration and memory and decreasing anxiety. Users feel energized and satisfied and they want more. The body quickly adapts to repeated nicotine exposures, and the brain, in a sense, rewires itself to compensate for the chemical imbalances imposed by the drug. When nicotine is withdrawn, the physiological adaptations remain, and the individual is left feeling extremely uncomfortable. Cravings, anxiety, depression, and irritability are all manifestations of nicotine withdrawal.

Although the health risks of smoking are well documented and generally associated with other toxins in tobacco, even small doses of nicotine are toxic, as evidenced by its use as a commercial pesticide. Symptoms of nicotine poisoning include nausea, vomiting, headaches, dyspnea, and seizures. It can be lethal, even in small doses, and children who ingest cigarettes are at the highest risk of toxicity.

Nicotine Replacement Therapy
Subsequent to a smoking ban instituted by the Royal Swedish Navy, submarine crewmen were observed as being ill-tempered and distracted as they coped with the affects of nicotine withdrawal. The Swedish government requested assistance from a pharmaceutical company, and in 1967 Ove Ferno, a researcher at Pharmacia (now merged with Pfizer), developed a nicotine replacement gum to placate the symptoms of withdrawal. It was registered as a pharmaceutical and made available to the general population in 1978. Nicotine replacement therapy (NRT) was thus born. NRTs are now available in numerous delivery formulations, and each has specific and unique applications. NRTs help relieve nicotine cravings without the carcinogens, carbon monoxide, and other toxins found in cigarettes.

Providing nicotine replacement therapy is both a science and an art. Although the benefits of NRTs are well documented in peer-reviewed journals, achieving optimal results is a challenge. Choosing the appropriate mix of NRTs and other pharmaceutical options and integrating them with an individualized quit plan is a skill that benefits from experience. Unfortunately, many clinicians have neither the inclination, the time, nor the training to work with the patient to achieve the desired outcome. Only about half of current smokers recall having been asked about their smoking status, or being urged to quit by a doctor.¹ And a majority of US medical school graduates are not adequately trained to treat nicotine dependence.^2-4 Nursing and respiratory therapy schools are just beginning to integrate smoking cessation into the curriculum.

Nicotine gum is used in place of cigarettes as soon as the patient stops smoking—10 to 15 pieces a day is typical. It is essential that patients be instructed in correct technique for using the gum to avoid releasing the nicotine too rapidly. Nicotine inhalers utilize a plastic cylinder containing a cartridge that delivers nicotine when the user puffs on it. The cartridges last for about 20 minutes of active puffing. It offers a convenient and feasible alternative to cigarettes for patients who are not ready or willing to abruptly quit. Nicotine lozenges release small amounts (2 mg and 4 mg) of nicotine that is absorbed in the mucosa of the mouth and gums. It should be allowed to dissolve slowly—not chewed or swallowed. Nicotine nasal spray delivers nicotine to the nasal membranes, and reaches the bloodstream faster than any other NRT formulations.

The ubiquitous nicotine patch enables patients to control cravings and withdrawal symptoms while they transition to a nonsmoking status. It is commonly available in 5 mg, 10 mg, and 15 mg dosages, which are released over a 16- to 24-hour period and may or may not be removed at night (depending on brand). The patch is composed of three layers: a backing layer on top, a middle layer containing the pharmaceutical, and a bottom layer that releases the drug into the skin. Although treatment regimes vary, patients typically begin by taking the largest dose for approximately 8 weeks, while they deal with the psychosocial aspects of quitting. They subsequently transition to the lower doses for 2 weeks at a time, so that they are finished with the course of therapy in about 3 months. Although the net amount of nicotine delivered is less than with active smoking, the patient experiences a steady dose of nicotine in the blood without the swings in level associated with smoking. Itching and redness are the most common side effects. Patch sites should be rotated daily.

As with cigars, cigarettes, and chew, NRTs should not be used by pregnant or nursing mothers. Nicotine is associated with increased miscarriage, it is known to be harmful to fetal development, and it passes into breast milk. Although NRTs can be combined with other forms of pharmacotherapy, patients should obviously avoid smoking while using the nicotine replacements. Unlike many other pharmaceuticals, NRTs need to be used as part of a comprehensive and ongoing care plan that includes counseling and follow-up.

Bupropion
Bupropion is primarily recognized as an antidepressant, and was initially marketed for that purpose. The mechanism of action is not well understood, but it is theorized that its dopaminergic and noradrenergic actions could be responsible for its efficacy in smoking cessation. Repeated use of bupropion, even among patients who had previously used bupropion in failed smoking cessation attempts, can be successful. One study demonstrated that 27% of participants receiving bupropion SR remained abstinent compared with 5% of participants receiving placebo.⁵ Patients should begin using bupropion 2 weeks before their quit date and continue using it for 6 months or more for best results. Experienced smoking cessation counselors frequently endorse the use of bupropion in conjunction with NRTs for maximum benefit.

Clonidine and Nortriptyline
Clonidine and nortriptyline are considered second-line pharmaceuticals for use in smoking cessation. Clonidine is primarily used to treat hypertension. Nortriptyline is approved by the US Food and Drug Administration (FDA) only as an antidepressant. Because nortriptyline produces sedation, patients should be careful when driving and using machinery.

Varenicline
Varenicline tartrate is a non-nicotine oral medication that is being tested for its effectiveness and safety in treating smoking addiction. It is not an NRT, but it binds to nicotine receptors in the brain, just as nicotine does, reducing the symptoms associated with withdrawal from nicotine. Varenicline also dampens the effect of nicotine in case a smoker has a relapse and smokes a cigarette. Researchers hope that the dual action will make it a more effective treatment for helping people quit smoking. The FDA has granted a 6-month priority review for a New Drug Application. The continuing studies on varenicline will explore dosage, possible side effects, and optimal use of the medication. Long-term success rates are the gold standard for any smoking cessation aid, however, and varenicline remains unproven in large groups over the long term.

Rimonabant
An exciting new drug that has been shown to reduce body weight and improve cardiovascular risk factors in obese patients6 has also showed promise for use in smoking cessation. Rimonabant is a member of a new class of drugs called selective cannabinoid-1 blockers. STudies with Rimonabant And Tobacco USe (STRATUS-US), conducted at the University of Cincinnati College of Medicine, showed rimonabant doubled the odds of quitting smoking compared with placebo, markedly reduced postcessation weight gain at 10 weeks, and was well tolerated.⁷ However, when the FDA recently issued approval for the drug in treating obesity, it excluded approval for use in smoking cessation. The promise of a drug that could be simultaneously efficacious in treating two major cardiovascular risk factors—smoking and obesity—has naturally created considerable anticipation. Long-term risk/benefits and the ability of the drug to become the long-awaited “magic bullet” for smoking cessation are far from being realized, though.

Conclusion
Pharmaceutical support for smoking cessation continues to evolve, and the growing body of peer-reviewed studies combined with practical experience has made treatment options for nicotine addiction more flexible than ever. Double-blind, placebo-controlled trials of pharmacological cessation aids have revealed varying and conflicting degrees of success. While patients and clinicians alike might wish for a pharmaceutical solution to the complex process of smoking cessation, a more sophisticated understanding of the problem suggests there may never be an easy fix. In addition to overcoming the powerful physical addiction of nicotine, smokers are faced with essential social and psychological hurdles that must be addressed. Long-term success includes changing their mind-sets and self-identities from “smokers” to “nonsmokers.” Pharmaceuticals are important tools but will likely never replace the toolbox of resources required for successful long-term smoking cessation.

John A. Wolfe, RRT, CPFT, is clinical specialist, North Colorado Medical Center, Greeley

References
1. Smoking Cessation Clinical Guideline Panel and Staff. The Agency for Health Care Policy and Research Smoking Cessation Clinical Practice Guideline. JAMA. 1996;275:1270-80.

2. Ferry LH, Grissino LM, Runfola PS. Tobacco dependence curricula in US undergraduate medical education. JAMA. 1999;282: 825-9.

3. Krupski WC, Nguyen HT, Jones DN, Wallace H, Whitehill TA, Nehler MR. Smoking cessation counseling: a missed opportunity for general surgery trainees. J Vasc Surg. 2002;36:257-62; discussion 262.

4. Spangler JG, George G, Foley KL, Crandall SJ. Tobacco intervention training: current efforts and gaps in US medical schools. JAMA. 2002;288:1102-9.

5. Gonzales DH, Nides MA, Ferry LH, et al. Bupropion SR as an aid to smoking cessation in smokers treated previously with bupropion: a randomized placebo-controlled study. Clin Pharmacol Ther. 2001;69:438-44.

6. Pi-Sunyer FX, Aronne LJ, Heshmati HM, Devin J, Rosenstock J; RIO-North America Study Group. Effect of rimonabant, a cannabinoid-1 receptor blocker, on weight and cardiometabolic risk factors in overweight or obese patients. JAMA. 2006;295:761-75.

7. Nicotine addiction: Rimonabant helps smokers quit while limiting post-cessation weight gain. Respiratory Therapeutics Week. April 12, 2004:27. Available at: www.newsrx.com/issuearticle/Respirtory-Therapeutics-Week/2004-0412/0412200433330RT.html _ Accessed March 9, 2006.