Pfizer halts global Chantix distribution after testing flags impurities

Smokers looking for Pfizer's cessation med Chantix may have a tough time finding the drug as the pharma giant has halted global distribution on impurity concerns.

After finding unacceptable levels of potential carcinogens called nitrosamines in certain Chantix lots, Pfizer has halted worldwide distribution of the popular smoking cessation medicine. 

A spokesman said the company believes 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." Varenicline is the generic name for Chantix.

The issue seems to stem back to the high-profile global recalls of valsartan and metformin in recent years. Global drug regulators have been asking companies to monitor for impurities that can occur in certain medicines, and Pfizer's internal testing turned up unacceptable levels in some Chantix batches. Pfizer is pausing worldwide distribution of the medicine as a result and is speeding up its internal testing.

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Everyone is exposed to nitrosamines in daily life, but regulators have been trying to get a handle on medicines that may expose consumers to unsafe levels

"We have worked hand-in-hand with regulatory authorities around the world who are taking varying approaches and have varying timelines," Pfizer's spokesman said. "All information has been communicated publicly per guidance from regulatory authorities."

Wednesday, the Korea Biomedical Review reported that Pfizer's Korea unit informed distributors that certain doses were out of stock. Officials in Canada have posted a notice about a recall, as well.

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In recent years, a host of drugmakers have had to recall batches of blood pressure and diabetes drugs valsartan and metformin, respectively, after testing turned up evidence of an impurity called NMDA. The impurity can develop during the manufacturing or storage of the widely used drugs. Regulators have said NMDA, a type of nitrosamine, can be carcinogenic after long-term exposure.

Pfizer's Chantix generated $919 million last year. The drug lost U.S. patent protections in November.