Pfizer's Study Raises Issues with Chantix

Last Thursday I discussed the recent Institute for Safe Medication Practices report showing a high level of serious adverse events associated with Chantix (varenicline). Since then I became aware of a Pfizer-funded study comparing the safety and effectiveness of Chantix and nicotine replacement therapy in the form of a patch.

The study, published online in Thorax in early February, was a 52-week randomized trial in which participants received either Chantix for 12 weeks or a nicotine patch for 10 weeks. Participants (376 in the Chantix group and 370 on the patch) received counseling at every telephone and clinic visit. Persons with a history of depression or other psychological disorder and a host of medical conditions were excluded.

The self-reported "continuous abstinence rate" (CAR), confirmed by measuring exhaled carbon monoxide, for the last 4 weeks of treatment was 55.9 percent for Chantix (weeks 9-12) and 43.2 percent for NRT (weeks 8-11). CAR through week 52 was 26 percent for Chantix and 20 percent for NRT, with the difference just missing statistical significance. Since all participants in the trial received intensive counseling to help them stop smoking, these percentages are higher than what can expected in the real world.

Adverse events were experienced by 84.8 percent of the Chantix group and 70.3 percent of the NRT group with severe adverse events were experienced by 9.8 percent of the Chantix group and 7.3 percent of the NRT group. Two patients in the Chantix group experienced serious depression or suicidal ideation.

This study was too small and excluded too many categories of patients to give a full picture of Chantix's side effect profile. Some general observations seem warranted, however.

1. Patients in the Chantix group experienced significantly more side effects, including serious side effects.

2. At the end of 12 months, the advantage in effectiveness for Chantix was relatively minor.

-- PM