A physician and top smoking cessation researcher says U.S. regulators and a drugmaker brushed aside his concerns a year ago about possibly dangerous side effects from longer-term use of the stop-smoking drug Chantix.
Now a new report from the nonprofit organization Institute for Safe Medicine Practices cites nearly 1,000 adverse event reports associated with Chantix. That report, released late last month, has prompted the Federal Aviation Administration to ban the drug's use among commercial pilots.
The report was the first time many people had heard of the possible pitfalls of a drug considered largely safe for the treatment of nicotine addiction, and for which over 6 million prescriptions have been written. The controversy over Chantix and the persistence of the complaining doctor, John Spangler, director of Tobacco Intervention Programs at the Wake Forest University School of Medicine in Winston-Salem, N.C., points up loopholes and gaps in the way drugs are declared to be safe to use in the United States. Spangler has contributed articles to ABCNews.com in the past.
Spangler as early as May 2007 raised questions over the adequacy of the long-term safety of Chantix. He raised concerns about heart and vision effects in people who took the drug for at least one year. He brought them to the attention of the medical community, the U.S. Food and Drug Administration and Pfizer, the company that manufactures the drug.
At the center of these concerns was a study that purported to record side-effects of the drug, also known as varenicline, when used for an entire year.
Spangler says the safety study by researchers employed by Pfizer and published in a relatively obscure medical journal looked at far too few subjects — a total of only 251 taking the drug — to determine whether or not the drug is safe when used over that duration.
Yet, the conclusion of the study reads, "Varenicline 1 mg BID can be safely administered for up to 1 year" — a conclusion, Spangler says, that is not supported by the data.
"[Making this conclusion] would be like me balancing my checkbook without looking at any of the checks I wrote or the deposits I made," Spangler says. "They've got to look at the data."
Furthermore, Spangler says when he analyzed the data in the Pfizer study, he found that the authors ignored possible signals of safety concerns.
"When I did the inferential calculations, I found a relationship [to serious adverse effects]," he says. "They had the data, but they didn't crunch the data at all."
The authors failed to mention that study subjects who took the drug were 2.5 times as likely to experience a serious adverse event, Spangler says. The FDA defines an adverse event as including such problems as hospitalization, a persistent or significant disability or incapacity, or congenital anomaly or birth defect.
While these serious medical events could be due to chance, the small size of the study makes it impossible to draw any firm conclusion, he added. So until a larger study of the same duration proves otherwise, medical professionals must consider the possibility that this increased risk exists.
Pfizer officials counter that even though the study concludes that it is safe to take the drug for 52 weeks straight, the package labeling suggests a course of 12 weeks to help smokers quit, followed by another 12-week course to help patients continue their abstinence.