New Drug Helps Smokers Kick the Habit
For smokers who want to quit, a drug called varenicline increases the odds of success threefold compared to a placebo pill, according to a new review of studies. The drug also improves quit rates compared to an antidepressant that is commonly prescribed as a smoking cessation aid.
Varenicline, sold under the trade name Chantix by drug manufacturer Pfizer, is the first new FDA-approved drug for smoking cessation in the past decade. It is also the first drug designed to interact with a key brain receptor involved in addiction to nicotine.
"Varenicline is quite high-tech," said lead author Kate Cahill of Oxford University. "It's safe and it looks to be effective, so I think it's quite important."
Varenicline helps maintain levels of a feel-good brain chemical called dopamine, counteracting withdrawal symptoms and reducing craving. It is the third drug-based approach licensed for prescription to smokers who are trying to quit. Nicotine replacement therapy has been available for more than 20 years. The antidepressant bupropion (Wellbutrin, Zyban) was approved as a smoking cessation aid in 1997.
The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
The reviewers identified five studies that tested the effectiveness of varenicline against a placebo in smokers attempting to quit. Three of these studies also compared the effectiveness of varenicline against bupropion. A sixth study tested the effectiveness of varenicline in reducing relapse rates among successful quitters. Almost 5,000 participants were enrolled in these trials.
In the combined studies, varenicline increased the odds that participants would avoid taking even a single puff on a cigarette at 12 months, compared to participants who received a placebo. In the three studies comparing varenicline to bupropion, the new drug outperformed bupropion in improving the chances of achieving continuous abstinence at 12 months.
All except one of the studies used a biochemical test to verify that smokers were abstinent.
The most common side effect of varenicline was mild to moderate nausea, which tended to decrease over time. There were no serious adverse events with the drug.
"One of the major findings of our review is that the drug looks to be safer than bupropion," Cahill said. "Bupropion has something like a one-in-a-thousand risk of seizures. We can only go on what we've seen so far, but apart from nausea, varenicline doesn't seem to have any serious problems, and it's been prescribed since last May in the States without any sort of horror stories coming out."
Cahill called the trials "well conducted" and "very high quality."
While all of the trials were funded and managed by the drug's manufacturer, Cahill said this is the pattern for any new drug. "The first trials tend to be run by the drug companies themselves because they're trying to get the drug licensed."
Steven Schroeder, M.D., who heads the Smoking Cessation Leadership Center at the University of California, San Francisco, agreed that "it's very hard nowadays to get any clinical trial of any drug that isn't funded in that way." More of a problem, he said, "is that trials tend to be done under very controlled circumstances with relatively small numbers."
The studies in the review excluded smokers with psychiatric disorders, recent cardiovascular disease and other health problems. To enhance the odds of success, smokers received brief counseling sessions and phone calls throughout the studies.
How well the new drug would do without counseling hasn't been tested, said Schroeder. "And it would be nice to know how this drug acts in the mental health population, where the rate of smoking is extremely high."
But these caveats aside, Schroeder said the availability of varenicline will have an important side benefit: "The message is going to go out to smokers that there's a new way to quit, and since most smokers want to quit, they may be stimulated to try the new Pfizer drug or another drug or quit on a cold turkey basis. All that is excellent news for the health of the public."
The reviewers concluded that, based on the one trial of varenicline to prevent relapse in successful quitters, the effectiveness of the drug as an aid to relapse prevention "has not been clearly established."
The review also identified one trial of a smoking cessation aid called cytisine, which was developed from the golden rain tree by Bulgarian researchers in the 1960s and was the basis for the development of varenicline in the 1990s. The trial showed that smokers randomized to cytisine were more likely to report that they were abstinent at a two-year follow-up compared to placebo users. However, the reviewers called the evidence on cytisine "limited at present."