Pfizer is recalling batches of its anti-smoking medication Chantix after an increased level of impurities that can cause cancer were found in the drug.
Included in the nationwide recall are two lots of Chantix 0.5mg Tablets, two lots of Chantix 1 mg Tablets, and eight lots of a Chantix kit of 0.5mg/1 mg Tablets, the drug manufacturer announced on Friday.
All are "due to the presence of a nitrosamine, N-nitroso-varenicline, above the Pfizer established Acceptable Daily Intake (ADI) level," the company said in its recall announcement.
"Long-term ingestion of N-nitroso-varenicline may be associated with a theoretical potential increased cancer risk in humans, but there is no immediate risk to patients taking this medication," they added. "The health benefits of stopping smoking outweigh the theoretical potential cancer risk from the nitrosamine impurity in varenicline."
N-nitroso-varenicline belongs to a class of compounds called nitrosamines, some of which have been classified as "possible human carcinogens" by Food and Drug Administration (FDA).
Everyone has been exposed to some level of nitrosamines, which are common in water and foods, according to the FDA. However, nitrosamine impurities may increase the risk of cancer if people are exposed to them above acceptable levels and over long periods of time.
In an update on Friday, the FDA recommended that patients who have been prescribed drugs affected by the recall to "continue taking their current medicine until their pharmacist provides a replacement or their doctor prescribes a different medication that treats the same condition."
"Agency scientists evaluated the risk of exposure to N-nitroso-varenicline at interim acceptable intake levels up to 185 ng per day 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 level," the FDA said.
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Chantix is a treatment that helps patients to quit smoking and is intended for short-term use.
Nine lots of the drug were recalled from warehouses by Pfizer earlier this month after the company found that the medication may contain levels of N-nitroso-varenicline above FDA's acceptable intake limit, according to the agency.
"In addition to the voluntary recall, Pfizer is holding release of varenicline to the U.S. market until it can confirm N-nitroso-varenicline levels below what the company considers to be acceptable," the FDA said in a statement released on July 2.
"FDA is actively considering options to help mitigate a shortage of varenicline in the U.S. including working to identify an alternate supplier," they also said. "The agency is continuing to investigate the presence of N-nitroso-varenicline in varenicline products and will provide more information as it becomes available."