To ensure uninterrupted access to varenicline, the US Food and Drug Administration (FDA) will allow distribution of the smoking cessation drug to continue; some lots of pills were found to contain the carcinogen N-nitrosodimethylamine (NDMA).
On July 2, the FDA alerted patients and healthcare professionals of Pfizer's voluntary recall of nine lots of varenicline (Chantix) because of the possibility that the tablets contained levels of the nitrosamine impurity that were higher than the FDA's acceptable intake limit.
On July 16, the FDA said it would not object to distribution of varenicline that contained levels of the nitrosamine impurity higher than its acceptable intake limit of 37 ng/d but lower than the interim acceptable intake limit of 185 ng/d until the impurity can be eliminated or reduced to acceptable levels.
"N-nitroso-varenicline may be associated with a potential increased cancer risk in humans, but there is no immediate risk to patients taking this medication," the FDA said in an update on its website.
"An increased cancer risk would be associated with long-term use, and the health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline," the FDA said.
By allowing Canadian generic drugmaker Apotex to temporarily continue to distribute varenicline in the United States despite the possibility that tablets containing N-nitroso-varenicline at levels up to the FDA's interim acceptable intake limit of 185 ng/d "will help maintain adequate varenicline supply in the US for the near term," the FDA said.
An evaluation by FDA scientists found that the risk of exposure to the carcinogen at this level presents "minimal additional cancer risk" compared with a lifetime exposure at the 37 ng/d level, the FDA said.
"The health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline," the agency added.
The FDA encourages healthcare professionals to report any adverse reactions with varenicline to the agency's MedWatch program.
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Cite this: FDA Allows Impure Smoking Cessation Drug to Stay on the Market - Medscape - Jul 19, 2021.