Pfizer warns of potential carcinogen in Viracept

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Pfizer has issued a “Dear doctor” letter warning healthcare professionals of the presence of a potential carcinogen in Viracept and cautioning against its use in pregnant women and pediatric patients, FDA said.

Pfizer said pediatric and pregnant women patients should not be started on Viracept until further notice. While pregnant women should be switched to an alternate therapy, the company said, “FDA and Pfizer agree that the benefit-risk ratio remains favorable” for pediatric patients already on the drug.

The chemical, ethyl methanesulfonate (EMS), is a process-related impurity formed during manufacture of the drug that has been found to be teratogenic, mutagenic and carcinogenic in animals, though no data from human studies exists. The presence of EMS in heightened levels prompted Roche, which manufactures Viracept in Europe, to pull the drug from all EU markets in June. Pfizer said it tested all active ingredients and found levels substantially lower than those that prompted the Roche recall. The problem with the Roche drug was detected when the company received reports of tablets exuding a strange odor.

Separately, Pfizer chairman and CEO Jeff Kindler said yesterday at the Bear Stearns Healthcare Conference that the company expects Lipitor sales to be flat or down up to 5% on last year's numbers due to competition from generic Zocor (simvastatin). The company also announced it is closing its Sandwich, UK manufacturing plant and shedding 420 jobs as part of its ongoing cost-cutting efforts, though which it aims to cut 10% of its workforce by 2009.

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