Pfizer yanks 12 Chantix lots on carcinogen concerns after pausing global shipments last month

Pfizer paused global distribution of Chantix last month after flagging unacceptable levels of potential carcinogens called nitrosamines in some batches. (Pfizer)

Pfizer, which put global Chantix distribution on hold late last month, is escalating its response to discovering a potential cancer-causing agent in the drug.

Pfizer has recalled 12 Chantix tablet lots with levels of the likely carcinogen N-nitroso-varenicline—a type of nitrosamine—above Pfizer's pre-set Acceptable Daily Intake (ADI) level, the company said in a notice posted on the FDA's website. The move expands on a recall—covering 9 lots—issued to warehouses last week.

Pfizer's version of the drug, which also goes by the generic moniker varenicline, is currently in shortage in the U.S. The company in June said it would pause shipments worldwide over nitrosamine concerns, though a spokesperson at the time said Pfizer believed the drug's benefits "outweigh the very low potential risks, if any, posed by nitrosamine exposure from varenicline on top of other common sources over a lifetime." 

Pfizer's recall covers two 0.5 mg tablet lots; two 1 mg lots; and eight lots of a Chantix kit that includes both 0.5 mg and 1 mg doses, the company said. The company shipped the products throughout the U.S. and Puerto Rico between June 2019 and June 2021.

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Nitrosamines are everywhere, Pfizer points out. They're common in water and foods such as dairy products, vegetables and grilled and cured meats. Everyone is exposed to nitrosamines in some capacity, which can increase the risk of cancer if a person is exposed to excessive levels over time, the company said. Chantix is intended for short-term use, Pfizer said in its recall notice. 

Pfizer maintains that there's "no immediate risk to patients taking this medication," and adds that the perks of quitting smoking outweigh the potential dangers from nitrosamine impurities. The company believes Chantix's risk/benefit profile "remains positive" and it has urged patients to call on their doctors for an alternative treatment if they received Chantix from one of the suspect lots. 

For its part, the FDA says patients taking recalled varenicline should "continue taking their current medicine until their pharmacist provides a replacement or their doctor prescribes a different medication that treats the same condition." 

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To ease the Chantix shortage, the FDA is allowing certain manufacturers to temporarily distribute varenicline tablets with N-nitroso-varenicline above the FDA's acceptable intake limit of 37 ng per day but below an interim limit of 185 ng a day "until the impurity can be eliminated or reduced to acceptable levels."

Specifically, the regulator has called on Apotex, which distributes varenicline in Canada, to export its generic Apo-Varenicline tablets to the U.S. Pfizer's branded version generated around $919 million last year and lost U.S. patent protections in November. It's not clear whether other generics companies have been cleared to launch in the U.S.

Over the past few years, a slate of drugmakers have had to recall valsartan blood pressure meds and metformin diabetes drugs over the presence of another type of nitrosamine called N-Nitrosodimethylamine (NDMA). 

In the case of metformin, the FDA pressed five companies to pull extended-release products last May. In the months that followed, several of those drugmakers expanded their recalls, while host of additional companies joined the list. Some of those metformin impurity concerns have stretched into 2021.