Following a recent report by a non profit drug safety group about newly found serious side effects linked to Pfizer’s smoking cessation drug Chantix, a spokesman for the Federal Aviation Administration, part of the US Department of Transportation, told the press yesterday, Wednesday, that the agency would be introducing a ban to stop private and commercial pilots and air traffic controllers from taking the drug.

According to Reuters news agency, FAA spokesman Les Dorr, said:

“It’s prudent to deem the drug no longer acceptable for use.”

The FAA gave approval for pilots to use Chantix (varenicline) in July 2007. This was before the US Food and Drug Administration (FDA) asked the manufacturer Pfizer, in November 2007, to change the label to show that post marketing reports were describing patients experiencing serious adverse events after taking Chantix to stop smoking. The serious adverse events were described as “suicidal thoughts and aggressive and erratic behavior”.

Although the FAA was planning to re-assess Chantix itself, it decided to issue this ban on the evidence presented by the Pennsylvania-based Institute for Safe Medication Practices (ISMP) whose researchers investigated the adverse event reports with scientists from Wake Forest University.

According to the Wall Street Journal, the agency sent letters yesterday, telling pilots who were using Chantix to stop, and not to fly for 72 hours.

The ISMP report reviewed adverse events reports sent to the FDA by doctors and patients and found that during the fourth quarter of 2007 there were 988 serious incidents associated with the use of Chantix by US patients. This is more than for any other drug reported in that same time frame.

The report also highlighted the fact that while previously, it was revealed that Chantix had been linked to psychiatric problems such as suicidal thinking and depression, based on the more recent reports, it appeared that patients using Chantix were also experiencing other serious adverse events such as heart problems, seizures and diabetes.

The ISMP report found 173 types of injury linked to Chantix use, including falls and traffic accidents, possibly because the patients involved had muscle spasms, confusion and dizziness after taking Chantix.

The report also highlights hundreds of other reports received by the FDA that mention hearth-rhythm problems, movement disorders, and blood sugar disorders, including diabetes.

The lead author of the study, ISMP’s senior drug safety expert, Thomas Moore told the Wall Street Journal that the FDA and Pfizer should strengthen Chantix label warnings further and look into the emerging safety issues, calling the existing warnings “completely inadequate” in the light of the new findings.

The Journal points out that Moore’s study, which has not been published in a peer reviewed journal because he wanted to get the information in the public domain as soon as possible, has some weaknesses. Because the study only examines adverse event reports, it cannot say for certain that Chantix caused the adverse reactions, and there is also potential bias in that the reports are filled in by doctors, patients and even sometimes the patients’ lawyers.

Pfizer said the label on Chantix already warns patients not to drive or use heavy machinery until they know how they are going to be affected by the drug, and it already lists the conditions raised by Moore, such as diabetes, cardiac arrhythmia, impaired motor skills, and so on, as rare occurrences that have to be taken into account when deciding the risks versus the benefits of the drug for the individual patient.

Pfizer’s senior vice president for safety and risk management, Gretchen Dieck, said it was very difficult to unravel the effect of the drug from the effect of nicotine withdrawal:

“When you’ve got the nicotine withdrawal along with Chantix, it’s just very difficult to tell what is causing it,” she said, as reported by Reuters.

Reuters also reported that FDA spokeswoman Susan Cruzan said the federal agency was still investigating Chantix’s psychiatric effects, and that while wider reviews were desirable, the “FDA currently does not have adequate staffing to conduct such reviews.”

Nicotine is addictive because it attaches to receptors in the brain that trigger the release of dopamine, creating a pleasurable feeling that soon falls away, causing the smoker to crave another “rush”. Giving up smoking is hard because the smoker feels miserable and down without the comforting pleasure of the dopamine rush. This causes irritability and concentration difficulties, and can last for several months after quitting.

Products that replace nicotine, like patches, gum, lozenges, and some anti-depressants, are thought to help people quit because they stimulate the release of low levels of dopamine, easing the withdrawal process.

Chantix also releases low levels of dopamine in the brain, but it is also thought to block the nicotine receptor from accepting the nicotine, thus breaking the link with the dopamine trigger.

Thus, if you lapse and have the odd cigarette, the theory is that by using Chantix, your brain receptors won’t be stimulated like before, and you won’t get that buzz from the dopamine, and smoking becomes less pleasurable.

In February this year, the FDA issued an alert to inform doctors and patients that it had asked Pfizer to move the information about the potential serious neuropsychiatric symptoms and events linked to Chantix to the more prominent WARNINGS and PRECAUTIONS section of the label. Before this, the information was in the less prominent POST-MARKETING EXPERIENCE section.

And earlier this month, the FDA also approved the new Medication Guide, which spells out early on, that:

“Some patients have had changes in behavior, agitation, depressed mood, and suicidal thoughts or actions while using CHANTIX to help them quit smoking.”

The guide also instructs the reader:

“If either you, your family or caregiver notice agitation, depressed mood, or changes in behavior that are not typical for you, or if you develop suicidal thoughts or actions, stop taking CHANTIX and call your doctor right away.”

Sources: Wall Street Journal, Reuters, Mayo Clinic.

Written by: Catharine Paddock, PhD