In a new advisory released yesterday, the US Food and Drug
Administration alerted health care providers, patients, and caregivers about
new safety warnings concerning Pfizer’s varenicline.
Varenicline, also known as Chantix, a pill prescribed for
those who want to quit smoking has been sold in United States from August 2006,
after it was approved in May 2006. Since its introduction, Chantix generated
about $600 million in sales.
In November last year the U.S. Food and Drug Administration
revealed that it had received reports of mood disorder and erratic behavior
among patients using Chantix.
FDA advised doctors to closely supervise their patients and
report whether they have any behavior changes.
Also, last month, Pfizer updated the Chantix label in US by
including a new warning that says the patients who are taking this drug should
be observed for serious neuropsychiatric symptoms, including changes in
behavior, agitation, depressed mood, suicidal ideation and suicidal behavior.
In its yesterday advisory, FDA said that a the agency's
review of the adverse event reports proceeds, it appears increasingly likely
that there may be an association between Chantix and serious neuropsychiatric
symptoms.
As a result, FDA has requested that Pfizer elevate the
prominence of this safety information to the warnings and precautions section
of the Chantix prescribing information, or labeling.
"While Chantix has demonstrated clear evidence of
efficacy, it is important to consider these safety concerns and alert the
public about these risks. Patients should talk with their doctors about this
new information and whether Chantix is the right drug for them, and health care
professionals should closely monitor patients for behavior and mood changes if
they are taking this drug," said Bob Rappaport, M.D., director of
the FDA's Division of Anesthesia, Analgesia and Rheumatology Products.
"We've become increasingly concerned as we've seen
there are a number of compelling cases that truly look as if they are the
result of exposure to the drug," he added.
Varenicline relieves withdrawal symptoms and tobacco craving
associated with smoking cessation by acting as an agonist for α4β2
nicotine receptors in the brain, which are associated with nicotine dependence.
At the same time, if a person smokes a cigarette while receiving treatment,
Champix acts as an antagonist to inhibit nicotine from binding to α4β2
nicotine receptors, restricting the patient’s sense of satisfaction associated
with smoking.
“Health care professionals, patients, patients' families,
and caregivers should be alert to and monitor for changes in mood and behavior
in patients treated with Chantix. Symptoms may include anxiety, nervousness,
tension, depressed mood, unusual behaviors and thinking about or attempting
suicide. In most cases, neuropsychiatric symptoms developed during Chantix
treatment, but in others, symptoms developed following withdrawal of
varenicline therapy,” noted FDA in its advisory.
Although it has agreed to include the warning since
November, Pfizer officials repeatedly said that there is no scientific evidence
linking Champix to depression.
“A causal relationship between Chantix and these reported
symptoms has not been established. In some reports, however, an association
could not be excluded. More specifically, some reports may have been
complicated by the symptoms of nicotine withdrawal in patients who stopped
smoking, but not all patients with these symptoms had quit smoking,” Pfizer
said in statement released last month.
In December last year, the European Medicines Agency (EMEA)
said Pfizer’s Champix, (the European name of Chantix), should carry a warning
about the high risk of suicide attempts among patients. The Committee for
Medicinal Products has closely monitored the safety of the drug for Human Use
(CHMP) since it was first authorized in the European Union in September 2006.
Meanwhile, on January 25, Pfizer Japan announced that the company
received manufacturing and marketing authorization for Champix.
