Chantix (varenicline) Safety

Last week a report was released by an organization called the “Institute for Safe Medication Practices” (ISMP) which claimed to have safety concerns about Chantix (varenicline, also marketed as Champix outside the United States). The Executive Summary of the report made two main recommendations:

1. Chantix should be avoided or used with caution by persons operating aircraft, motor vehicles or other machines (e.g. power stations) where a lapse in alertness or motor control could have serious consequences.
2. Patients and doctors should excercise caution in the use of Chantix (generally) and “consider the use of alternative approaches to smoking cessation.”

Given that most of us drive a vehicle, the report is basically suggesting that varenicline is such an unsafe drug that it should be avoided. These are strong recommendations, and have immediately resulted in the Federal Aviation Authority (FAA) and Federal Motor Carrier Safety Administration (FMCSA) adding varenicline to their list of drugs that should not be used by pilots or truck drivers. The report itself has not been published in a peer-reviewed journal and so it is reasonable to assess the quality of the data on which it was based, and to evaluate whether the recommendations are warranted on the basis of that data.

The ISMP report was based on an analysis of the frequency and type of serious adverse events that have been reported to the US Food and Drug Administration (FDA) about Chantix, in comparison to other drugs. In particular, the report noted that by the 4th quarter of 2007 Chantix “accounted for more reports of serious adverse events in the United States than any other drug.” This amounted to 988 reports about Chantix in the 4th quarter, as compared with 372 (Oxycodone) to 640 (Interferon Beta) reports about the next 5 most reported drugs.

The report then selected a sample (3063) of the total reports (excluding foreign or unclear reports) for slightly more detailed analysis. It noted that a much larger proportion of the reports about Chantix came from consumers (57%) than is typical of other drugs (26%) for which health professionals are the predominant source. The report also noted that a lower proportion of the reports about Chantix (2.5%) reported deaths, as compared with 17% of reports about other drugs.

The report summarized the most frequent medical terms included in the reports about Chantix. By far the most common term used was nausea (593), which was more than twice as common as any other reported symptom. It was also noteable that among the most commonly reported medical symptoms mentioned in the adverse event reports, many are also recognized nicotine withdrawal symptoms (i.e symptoms known to increase when smokers quit smoking, particularly without any treatment medication), such as depression (287), insomnia (242), anxiety (217), and weight increase (141).

Problems with the ISMP report and its conclusions

There are a number of fundamental problems with the quality of the data, analysis and interpretation in the ISMP report. Before discussing some of these, it is worth discussing the way that reports of serious adverse events are delivered to the FDA. There are 4 main sources of reports.

1. Members of the public can send reports directly to FDA, either by mail or via an on-line reporting system (and I have provided the link on previous posts on this blog about Chantix to ensure that reports reach FDA).
2. Health professionals can report adverse events to FDA.
3. Lawyers sometimes report adverse events to FDA.
4. The manufacturer is required to report to FDA any reports that are brought to its attention directly. Those adverse events that are already mentioned on the product labeling are reported on a quarterly basis, and novel symptoms must be reported within 15 days (expedited).

Reports from the first 3 of these sources are entirely voluntary and are made in a rather haphazard way. The ISMP report estimated that typically between 1 and 10% of serious adverse events are actually reported to FDA. It is commonly found that AE reports peak around two years after the launch of a drug, even if the drug becomes used more often thereafter. The purpose of the FDA’s reporting and monitoring system is to facilitate post-marketing surveillance and enable detection of patterns of adverse events that could potentially be caused by a medicine but were not detected in the initial placebo-controlled trials leading to drug approval. The main point here is that these reports are not made in a systematic way, and the frequency of reports can be influenced by factors such as (a) the frequency of use of the drug (b) the novelty of the drug (c) media coverage of the drug and (d) efforts by the company to interact with users in a manner that will lead to them hearing of and therefore being required to report on AEs.

With these factors in mind, here are some of the problems with the ISMP report:

1. The report fails to consider the frequency of the use of the drug when considering the number of adverse events being reported. Since its launch in August 2006 (i.e. less than 2 years), Chantix has been used by an estimated 5.5 million smokers in the United States. In 2007 alone it was used by 3.8 million new patients in the U.S. (6.2 million prescriptions). This is many times more than the other drugs listed in the ISMP report. For example, Etanercept (Enbrel, the drug with the 3rd largest number of adverse event reports to FDA) was launched in 1998, and has been used by a total of 450,000 patients WORLDWIDE in those 10 years. Comparing frequency of adverse events without adjusting for the frequency of drug use is so obviously inappropriate as to cast doubt on the reliability of the report as a whole.
As mentioned briefly in the ISMP report, many factors can affect the frequency of reporting of adverse events to FDA. In the case of Chantix, the widely publicized death of a rock musician (who was tragically shot by a neighbor in Texas) which his partner felt could have been related to Chantix, sparked off widespread media speculation about potential side effects. The manufacturer also offers a number of direct to consumer quit smoking services, including a free telephone hotline called “Get Quit”. Because this hotline is run by the manufacturer, whenever a caller mentions a symptom, they are immediately transferred to the medical department, the details are noted and the information reported to FDA. These events and procedures can have a large effect of increasing the number of serious adverse events reported and this was not adequately considered in the ISMP report. It is noteworthy that 92% of the events analyzed in the ISMP report came via the manufacturer.

2. The report fails to adequately consider the possibility that some of the reported adverse events may have been caused by nicotine withdrawal. The vast majority of those using Chantix were attempting to quit smoking, which itself is known to cause a range of nicotine withdrawal symptoms, including many of the symptoms most commonly reported to FDA and mentioned in the ISMP report (depression, insomnia, anxiety, weight increase). It is entirely plausible that many of these reported symptoms were caused by nicotine withdrawal rather than Chantix. In fact in the placebo-controlled trials of Chantix, withdrawal symptoms were REDUCED in those using Chantix.

3. The report doesn't adequately consider the serious health effects of tobacco dependence. The ISMP report characterizes the other comparison drugs as being “intended for serious illness in patients and have benefits that are accompanied by substantial risks. In comparison, varenicline is intended for use in healthy people to help stop smoking.” Unfortunately this statement indicates a misunderstanding of the nature of tobacco dependence as a serious illness causing the premature death of 50% of continuing smokers, and of the fact that a high proportion of patients using smoking cessation medications are already suffering from or at very high risk for smoking-caused illnesses, including some mentioned as adverse events in the report (e.g. cardiac arrhythmias).

4. The report inaccuratley characterizes the relative efficacy of varenicline versus other treatments. The ISMP report states that Chantix has similar long term quit rates to nicotine gum. This statement contradicts the findings of the new US Public Health Service Clinical Practice Guideline on Treating Tobacco Use and Dependence, which found a mean quit rate of 13.8% with placebo, 19% with nicotine gum and 33.2% with varenicline (p109) and that quit rates with varenicline are significantly greater than with the nicotine patch (p121). This Guideline, written after the recent labeling changes for varenicline, concluded that, “Varenicline is an effective smoking cessation treatment that patients should be encouraged to use.” (p113).

Probably the most basic problem with the ISMP report is its failure to consider the frequency of use of the medicines as a factor influencing the interpretation of the frequency of adverse events reported. It therefore remains unclear whether any of these serious adverse events were caused by varenicline. When added to the other problems of interpretation mentioned above, I prefer to rely on the recommendation of the US Clinical Practice Guideline, which resulted from a very thorough review of the available scientific evidence.

So what does this mean for patients considering quitting smoking? As always, rely on the advice of your own doctor rather than on reports in the media or the internet (including this one!).

The complete ISMP report can be found at:
Strong Safety Signal Seen for New Varenicline Risks

Previous posts on this blog that are relevant to this issue are:
What is nicotine withdrawal syndrome? 3/6/07
Ten tips for coping with nicotine withdrawal. 3/7/07
Chantix: how does this new stop smoking medicine work? 4/15/07
Can quitting smoking trigger depression? 6/16/07
Chantix and mental illness. 08/12/07
Two new studies of Chantix (varenicline). 08/19/07
Does Chantix cause mental health problems? 9/20/07
Chantix (varenicline) safety being reviewed by FDA. 11/21/07
New study of Chantix in comparison with NRT. 11/28/07
Smoking and suicide. 4/22/08

Full reports on the largest placebo-controlled trials of varenicline can be found via:
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About the Author

MA, MAppSci, PhD

Dr. Jonathan Foulds is an expert in the field of tobacco addiction.