The FDA is warning that the prescription smoking cessation medicine Chantix (varenicline) can change the way people react to alcohol. In addition, rare accounts of seizures in patients treated with Chantix have been reported. The FDA approved changes to the Chantix label to warn about these risks.
The FDA reviewed the case series submitted by Pfizer, the manufacturer of Chantix, as well as the 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, unusual or aggressive behavior, or they had no memory of things that happened.
In searching the FAERS database since the approval of Chantix (varenicline) in 2006, 48 cases of adverse events involving decreased tolerance to alcohol (n=11) or aggressive behavior (n=37) in patients taking Chantix and who also consumed alcohol were found. None of the cases of decreased alcohol tolerance reported that the amount of alcohol consumed was excessive for the individuals involved; before initiating Chantix, the same amount of alcohol had been consumed without the patients experiencing these adverse effects.
The outcomes included one case of decreased alcohol tolerance resulting in a motor vehicle accident with police arrest. In another case, the patient experienced a significant facial injury. For the 37 cases involving aggressive behavior, the amount of alcohol consumed while taking Chantix was insufficient to explain the event. In more than half of these cases, the patients described their behavior as a significant change from their behavior prior to Chantix treatment. Twenty-two cases reported harm to a person or property. Until patients know how Chantix affects their ability to tolerate alcohol, they should decrease the amount of alcohol they drink.
Amnesia was also reported following alcohol ingestion in patients taking Chantix. In most of the FAERS cases of decreased alcohol tolerance, as well as several submitted by Pfizer that were not identified in the FAERS search, patients described poor memory of their experience. In addition, in 16 of the 37 aggression cases (43%), patients reported no memory or impaired memory of their experience, and most of these 16 cases reported physical harm to a person and/or property.
Patients who have a seizure while taking Chantix should stop the medicine and seek medical attention immediately. The FDA searched FAERS and the medical literature and identified 64 cases of seizures in patients using Chantix. The median time to onset of seizure following starting Chantix was 2-3 weeks. In 37 cases, the patients had no history of seizure. Ten of these 37 cases had no contributing factors to the seizures other than Chantix. In the remaining 27 cases, other factors may have contributed to the seizures, including concomitant medications that can lower the seizure threshold, such as psychiatric medications. Of the 64 cases, 27 patients had a history of controlled seizures. Information about these risks has been added to the Warnings and Precautions section of the drug label and to the patient Medication Guide.
Also the FDA updated the Warnings and Precautions section of the label to include information about several studies that investigated the risk of neuropsychiatric side effects on mood, behavior, or thinking occurring with Chantix. These included observational studies, as well as analyses that Pfizer conducted of randomized controlled clinical trial data. Although the findings of the observational studies appear reassuring, they do not completely evaluate the effect of Chantix on neuropsychiatric adverse events and cannot be interpreted to mean that there is no risk of neuropsychiatric events with Chantix.
The limitations in these studies may underestimate the actual incidence of neuropsychiatric adverse events and restrict our ability to predict the direction of the relative risk associated with Chantix. The required postmarketing clinical trial that Pfizer is conducting was designed to include a more complete neuropsychiatric risk ascertainment, and therefore may provide a better understanding of these risks. The results of the trial are expected in late 2015.
See the FDA Drug Safety Communication
See also Medical Law Perspectives, May 2013 Report: Drugs, Dosage, and Damage: Physician Liability for Prescribing or Administering Medication
See also Medical Law Perspectives, August 2014 Report: Epilepsy and Seizure Disorders: Malpractice in Diagnosis and Treatment