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U.S. News

Pfizer Warns Health Care Professionals of Possible Carcinogen in HIV Treatment Viracept

September 11, 2007

On Monday, the Food and Drug Administration (FDA) announced that Pfizer Inc. has notified health care professionals that its HIV drug Viracept contains traces of ethyl methanesulfonate (EMS), a potential human carcinogen.

FDA has asked Pfizer to limit the presence of EMS, a process-related impurity, in Viracept. Animal studies have indicated EMS is carcinogenic; however, no human-based data are available.

Drug maker Roche in June recalled all packs of Viracept in Europe. Pfizer, which sells the drug in the United States, has not issued a recall here. Pfizer said testing has found EMS levels in its Viracept substantially lower than the levels that prompted the European recall by Roche.

Pediatric patients on stable HIV treatment plans may continue taking Viracept, but treatment-naïve patients should not begin regimens including Viracept until further notice. Pregnant women are advised not to start taking Viracept; those currently taking it should be switched to an alternative.

Pfizer is working with FDA on measures to keep EMS at substantially lower levels. For more information, visit

Back to other news for September 2007

Adapted from:
Associated Press

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This article was provided by CDC National Prevention Information Network. It is a part of the publication CDC HIV/Hepatitis/STD/TB Prevention News Update.
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