乌鸦传媒

Drugmaker Pfizer finally agreed to recall certain lots of its stop-smoking drug varenicline (Chantix) at the consumer level because of potential contamination with a nitrosamine compound, the .

More than 2 weeks ago, the FDA announced that Pfizer was recalling nine lots of varenicline at the warehouse level (i.e., before shipment to pharmacies). Tests had shown the presence of N-nitroso-varenicline, a potential carcinogen, in some samples. The agency said then that it had requested that Pfizer extend the recall to consumers, but the company had refused.

Varenicline is just the latest drug found to contain nitrosamines. Initially it was angiotensin receptor blockers (ARBs) such as valsartan, cropping up in the summer of 2018. The FDA set an allowable level of nitrosamines in these drugs, hypothesizing that the cancer risks were dose-related and would be low enough to be offset by the drugs' cardiovascular benefits, but a large number of recalls were initiated as well.

Then nitrosamines turned up in the popular antacid ranitidine (Zantac), leading the FDA to ask that all such products be pulled from the market -- with questions arising as to whether the contaminants originated at the factory or developed during storage, or even in vivo after patients ingested the pills. Nitrosamines were also detected in some tests on metformin samples, and a (one as recently as last month).

With regard to varenicline -- a drug that, unlike ARBs, antacids, or metformin, is not taken indefinitely -- the FDA emphasized that patients should not stop taking the drugs even if they come from the recalled lots until they can obtain safer replacements. "The health benefits of stopping smoking outweigh the cancer risk from the nitrosamine impurity in varenicline," the agency said.

Also, the FDA is temporarily allowing other manufacturers to distribute varenicline even with nitrosamine levels up to 185 ng/day, five times its previous allowable maximum of 37 ng/day. In particular, the ruling applies to a varenicline product distributed in Canada by Apotex, which may be imported during what is now a shortage situation. This, the agency said, "will help maintain adequate varenicline supply in the U.S. for the near term."

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