Pfizer has announced a recall of the anti-smoking treatment Chantix due to the presence of unacceptably high levels of N-nitroso-varenicline, a substance whose long-term use has been linked to a higher risk of cancer.
The drugmaker said on Sept. 16 that it is voluntarily recalling all lots of 0.5 mg and 1 mg Chantix tablets distributed in the United States, U.S. Virgin Islands, and Puerto Rico from May 2019 to September 2021.
The tablets were found to contain nitrosamine N-nitroso-varenicline at levels at or above levels deemed acceptable by the Food and Drug Administration (FDA).
Pfizer said that long-term ingestion of the substance “may be associated with a theoretical potential increased cancer risk in humans, but there is no immediate risk of patients taking this medication.”
“The health benefits of stopping smoking outweigh the theoretical potential cancer risk from the nitrosamine impurity in varenicline,” Pfizer said, adding that it believes that the safety profile of Chantix remains positive and it has not received any reports of adverse events linked to its use.
In order to lessen the impact of the recall on patients who rely on the drug to help them quit smoking, the FDA said in a follow-up notice on Friday that it will allow distribution of tablets containing N-nitroso-varenicline above the acceptable intake limit of 37 [nanograms] per day but below 185 ng per day “until the impurity can be eliminated or reduced to acceptable levels.” A nanogram is a billionth of a gram.
Echoing Pfizer’s position that the health benefits of quitting smoking outweigh the cancer risks from the varenicline impurities, the FDA said patients should continue taking their current verenicline medication until their doctor prescribes an alternate treatment or a pharmacist provides a replacement.
Pfizer’s Chantix saga began in July when the company recalled nine lots after finding they may contain nitrosamine above the FDA’s acceptable intake levels. At the time, the FDA similarly took a flexible stance around allowing the product to continue to be distributed in the interim.
The company later expanded its recall twice more to include a total of 16 lots, while the FDA said it was carrying out laboratory analyses to investigate the impurity.
“Agency scientists evaluated the risk of exposure to N-nitroso-varenicline at interim acceptable intake levels up to 185 ng per day (92.5 ppm) and determined that it presents minimal additional cancer risk when compared to a lifetime of exposure to N-nitroso-varenicline at the 37 ng per day (18.5 ppm) level,” the FDA said.
On Aug. 11, the FDA approved a therapeutically equivalent varenicline product manufactured by Par Pharmaceutical.