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Harvard Commentaries
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Reviewed by the Faculty of Harvard Medical School

Minding Your Mind Minding Your Mind

Quitting Smoking -- Benefits and Risks of Varenicline

July 10, 2012

By Michael Craig Miller M.D.

Harvard Medical School

Smoking is a huge cause of illness and death around the world and may be the toughest unhealthy habit to break. About a half-century after the Surgeon General's office released its first Report on smoking's dangers, smoking is still responsible for up to 1 in 5 deaths a year. Smoking caused perhaps 100 million deaths in the 20th century and a billion people may die prematurely in the 21st century as a result of its effects. Even for smokers who survive, their quality of life often suffers. So any treatment that can help people quit would be a tremendous benefit to public health, especially since almost three out of four smokers want to quit.

In 2006, the U.S. Food and Drug Administration approved a drug called varenicline (Chantix) as a quit-smoking aid. It was the first new anti-smoking drug to appear in 10 years. It is chemically similar to an extract from a European medicinal plant (Cytisus laburnum), which for many years had been used in Europe for smoking cessation. Although not a cure-all, varenicline may make quitters out of some smokers, according to the new research.

In the time since this drug has been in use, some data have suggested a link to an in-crease in suicidal behavior. In 2009, the FDA required that the manufacturer add a "black box" warning to the literature given to patients. This warning is similar to the warning now given about other neuroactive drugs (such as antidepressants or anti-seizure drugs).

The boxed warning states that anyone taking varenicline should be monitored for any change in mental state, such as suicidal thinking or a change in mood or behavior. Your doctor and you should take note of any worsening of a mental problem you already have.

The risks of the drug, of course, need to be weighed against the known high risks of smoking.

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How Varenicline Works

Nicotine "turns on" special receptors that triggers pleasure centers in the brain. The craving to smoke occurs when these receptors need more nicotine in order to be activated.

Varenicline works two ways. It partially imitates the effects of nicotine. By joioning with nicotine receptors, it cuts down craving and reduces withdrawal symptoms. But it also partially blocks the effect of nicotine. So, if a person taking varenicline smokes, the varenicline also reduces the rewarding sensations from nicotine in the ciagarette. The smoker gets less pleasure and is therefore less motivated to smoke. Studies have shown that varenicline is more effective than placebo at helping people quit. In one study, 44% of smokers quit with varenicline after 12 weeks compared with 17.7% of smokers who were given a placebo pill. Also, more people given varenicline were able to resist smoking after one year than people given a placebo pill.

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How to Take Varenicline

Since it takes a week or two to build up to the recommended dose of varenicline and reach a steady level in the bloodstream, it is a good idea to start treatment a week or two before your quit date.

The average dose of varenicline is 1 milligram twice per day. To minimize side effects, it is recommended that smokers start with 0.5 milligrams daily for the first week, then increase to twice a day. You can then gradually increase up to 1 milligram twice per day until you see results. As long as there are no adverse effects, you should continue the medication for about 3 months to give it a good test of how well it helps you avoid smoking.


An antidepressant drug called bupropion (Wellbutrin) was approved by the FDA in 1997 for smoking cessation under the name Zyban. It has helped some smokers quit, presumably because it triggers the same receptors that nicotine does. In some research, it has been better than placebo at helping smokers quit. Tricyclic antidepressants have also helped people quit. But bupropion and other antidepressants don't work for a huge number of smokers who want to quit. Bupropion carries a black box warning similar to the one for varenicline.

Take varenicline after a meal with a full glass of water. The drug has not been widely tested in patients who are taking other psychiatric medications, but so far few if any drug interactions — besdies those with nicotine — are known. Varenicline should not be taken with nicotine replacement products.

The most common complaint with varenicline is nausea. In studies, up to 30% of people taking the drug experienced it, though most people described the discomfort as mild and tending to improve over time. Other common side effects were headache, vomiting, gas, trouble sleeping, abnormal dreams and a change in taste perception. Quitting cigarettes still carries a problem many smokers dread — about a 7 to 8 pound weight gain, according to one study. Varenicline does nothing to prevent this problem.

Varenicline appears to work well compared with other smoking cessation treatments. But studies are somewhat disappointing: Only a minority of patients are able to quit smoking using this drug. Success rates in the real world tend to be even lower because patients in studies get much more support and education than people in the community. Also, researchers have yet to study the value of varenicline in patients with a significant psychiatric illness, among whom there is a notoriously high rate of smoking.

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Nicotine Replacement

For many years, the most common approach to helping smokers quit has been to give them replacement doses of nicotine. Nicotine, which stimulates the brain's reward centers, is the key addictive element in cigarettes. Smokers find it easy to keep their nicotine level up in their bloodstream by puffing at just the right rate. But as they do, the sensitivity of their nicotine receptors changes. They have to keep inhaling or pay the price by developing uncomfortable withdrawal symptoms.

Nicotine replacement therapy provides the nicotine without the carcinogens. Nicotene is available in a variety of forms, such as gum, lozenges, patches, sprays or inhalers. No matter which delivery system a smoker chooses, they all have about the same success rate. But that rate is certainly not high enough — fewer than one-quarter of people who use nicotine replacement manage to quit for good.

Nicotine replacement has its drawbacks. For one thing, more than one in three people become dependent on it. While exposure to pure nicotine is much less of a problem than smoking cigarettes, continued use can be risky for people with cardiac illness or for women who become pregnant.

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Worth the Effort

Because nicotine is so addictive, quitting smoking is very difficult. As with any addiction, behavioral aspects of treatment are important. Your readiness and motivation to quit are crucial elements of success. Even if varenicline reduces the physical craving and withdrawal symptoms, you'll be more likely to succeed if you have tools,(such as stress management or relaxation techniques), and support from friends and family to help you manage the inevitable discomforts and urges. See, for example, the American Lung Association's online smoking cessation support resources.

The concerns about suicide risk are important to keep in mind. The relative risk has so far been shown to be small, but it is wise to stay vigilant about any changes in mental state and report them to your doctor right away.

Varenicline represents a valuable additional treatment for tobacco addiction. Given the devastating effects of smoking, small gains in treatment can translate into millions of lives saved.

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Michael Craig Miller, M.D. is Editor in Chief of the Harvard Mental Health Letter. He is also associate physician at Beth Israel Deaconess Medical Center and assistant professor at Harvard Medical School. He has been practicing psychiatry for more than 25 years and teaches in the Harvard Longwood Psychiatry Residency Program.

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