Pfizer Inc.’s anti-smoking pill Chantix may receive new warnings from U.S. regulators after a study released today found the drug increased the risk of hospitalizations for heart problems by 72 percent.
The report, led by researchers at Johns Hopkins University, analyzed 14 Pfizer-sponsored drug trials with 8,216 patients and found about one new heart attack or similar disorder for every 400 patients taking Chantix. The U.S. Food and Drug Administration is examining the study and may consider new warnings, Curtis Rosenbraugh, director of the agency’s office of drug evaluation, said in an interview.
Chantix revenue has declined since the FDA warned in 2009 that the medicine may increase suicides and erratic behavior. Regulators last month added a warning for patients with a history of heart disease, based on a 700-patient study. The new analysis shows the greatest increased risk may be among patients with no signs of heart problems, said Sonal Singh, lead author of today’s study.
“I stopped prescribing Chantix several months ago, as soon as we found out about this data,” said Singh, a doctor and professor at Johns Hopkins University School of Medicine in Baltimore. “I’m not saying that nobody should use it, but I think people should have this information. They should decide whether the risk is acceptable to them.”
Chantix affects dopamine, a chemical in the brain involved in controlling mood and behavior. Because dopamine triggers a positive mood response, regulating its levels can remove some of the pleasure derived from smoking. The drug is the most effective pill to help smokers quit, and is about as effective as nicotine-replacement supplements available as patches, chewing gum, lozenges, nasal sprays and inhalers, Singh said.
“Pfizer disagrees with the interpretation of the data,” said Gail Cawkwell, vice president of medical affairs at New York-based Pfizer, in an e-mail. “The health benefits of quitting smoking are immediate and substantial. Pfizer strongly believes in and supports Chantix as an important treatment option.”
Chantix had sales of $755 million last year, down 14 percent from its high of $883 million in 2007, according to data compiled by Bloomberg.
The increased risk of heart problems while taking Chantix, if confirmed, doesn’t cancel out the benefits of taking the drug to quit smoking, J. Taylor Hays, a doctor who specializes in nicotine dependence at the Mayo Clinic in Rochester, Minnesota, wrote in an editorial published with Singh’s study in the Canadian Medical Association Journal.
“The worst outcome of this study would be for health-care providers to abandon” Chantix, Hays wrote. “The risk for serious cardiovascular adverse events is low and is greatly outweighed by the benefits of diminishing the truly heartbreaking effects of smoking.”
An FDA staff review from 2006 shows the agency was aware of a potential link between Chantix and serious heart complications. At the time, two researchers were asked to independently review each reported heart problem to rule out cases that were incorrectly reported or not related to the drug. On closer inspection, one reviewer said there was a 16 percent added risk of heart problems with Chantix, while the second reviewer found an 8 percent decreased risk, according to the staff documents.
“We saw a swing going anywhere from favorable to unfavorable,” said the FDA’s Rosenbraugh. “When you get results like that it’s hard to draw a definitive conclusion. It’s not something we would label.
“Dr. Singh has added to what we have seen and is helping to define the picture better,” Rosenbraugh said. “I’m not sure until we can further evaluate the study whether it’s going to change the label or not, but I can assure you this is something we’re very concerned about and are taking very seriously.”
Any risk from the Chantix needs to be evaluated against the benefits of quitting smoking, he said. The drug is taken for a short period of time to help people quit, while the significant health risks of continued smoking continue for a lifetime. For long-term smokers, more than half will die from complications related to their habit, according to a study of British doctors in 2004.
“We don’t want to send the message that people shouldn’t try to quit smoking,” Rosenbraugh said. “We just want to send the message that you should be cautious and look for cardiovascular symptoms should they occur.”
In the new heart study, 52 patients had serious cardiovascular complications among 4,908 patients taking Chantix, compared with 27 hospitalizations among 3,308 patients taking a placebo. The risk of Chantix complications was doubled for patients with no history of heart disease, Singh said.
The studies included in today’s report ranged from 7 to 52 weeks in duration. It’s not clear whether the added heart risk persists after treatment ends, Singh said.
GlaxoSmithKline Plc’s competing drug, Zyban, has been found to cause irregular heartbeats and increases in blood pressure in some patients, according to the FDA. The 700-patient study cited by the FDA last month was conducted by Pfizer to assess the risk of Chantix in patients with a history of heart disease.
That study found an increased risk of heart attack and chest pains, though the results weren’t statistically significant. The report prompted the FDA to seek a new analysis of all available trials using the raw data from the original research. That study will be completed by Pfizer within months, not years, the FDA’s Rosenbraugh and Pfizer’s Cawkwell said, without giving a specific time frame.