NEW YORK (CBSDFW.COM) — Pfizer is recalling all lots of its popular anti-smoking drug Chantix, because of possible high levels of a cancer-causing agent.

After pausing distribution of the drug in June and recalling specific lots of the medicine, the company took the action on September 17 of expanding the recall nationwide to include all 0.5 mg and 1 mg doses. Pfizer has asked wholesalers and distributors to immediately stop the use and distribution of the tablets.

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The recall is happening because the drug may contain levels of a nitrosamine, N-nitroso-varenicline, that is above the FDA acceptable limit. The company said long-term ingestion of N-nitroso-varenicline may be linked to a “theoretical potential increased cancer risk in humans.”

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The company said they are recalling the drug as a “precautionary measure” and that there was no immediate risk to patients taking Chantix. They are advising all users to consult their doctor to get recommendations and information about alternative treatments.

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Chantix was first approved by the FDA in 2006 as a prescription medication to help adults quit smoking. It’s typically used for between 12 and 24 weeks. Staff