The US Food and Drug Administration (FDA) has changed the labeling on the smoking cessation drug varenicline (Chantix, Pfizer Inc) to reflect concerns that the drug may lower tolerance to alcohol and is linked to a rare risk for seizures.
"Until patients know how Chantix affects their ability to tolerate alcohol, they should decrease the amount of alcohol they drink. Patients who have a seizure while taking Chantix should stop the medicine and seek medical attention immediately," the FDA warned in a release.
The new labeling is based on a case series submitted by Chantix manufacturer Pfizer, as well as cases in the FDA Adverse Event Reporting System (FAERS) database describing patients who drank alcohol during treatment with Chantix and experienced adverse reactions.
Some patients experienced decreased tolerance to alcohol, including increased drunkenness and unusual or aggressive behavior, or had memory loss.
The FDA reports that it also reviewed FAERS and the medical literature for cases of seizures with Chantix and identified cases in which the patients who had seizures while taking Chantix either had no history of seizures or had a seizure disorder that had been well controlled.
"In most of these cases, the seizures occurred within the first month of starting Chantix. Information about these risks has been added to the Warnings and Precautions section of the drug label and to the patient Medication Guide," the FDA notes.
The Warnings and Precautions section of the label have also been updated to include information about several studies that investigated the risk for neuropsychiatric side effects on mood, behavior, or thinking that occurred with Chantix.
"These included observational studies as well as analyses that Pfizer conducted of randomized controlled clinical trial data. These studies did not show an increased risk of neuropsychiatric side effects with Chantix, but not all types of neuropsychiatric side effects were examined, and the studies had limitations that prevented the FDA from drawing reliable conclusions," the FDA writes.
The FDA also notes in its release that it sent previous alerts about potential serious neuropsychiatric side effects with Chantix in 2009 and 2011, and these recent studies were discussed at an FDA Advisory Committee meeting in October 2014. The FDA adds that Pfizer is conducting a large clinical safety trial of Chantix to investigate this risk. Results from this study are expected in late 2015.
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Cite this: Chantix May Lower Alcohol Tolerance, Up Seizure Risk: FDA - Medscape - Mar 09, 2015.