FDA: Viracept may contain carcinogen ethyl methanesulfonate (EMS)

Pfizer issued a Dear Healthcare Professional Letter to inform healthcare professionals of the presence of ethyl methanesulfonate (EMS), a process-related impurity in Viracept and to provide guidance on the use of Viracept in pregnant women and pediatric patients.

EMS is a potential human carcinogen. Data from animal studies indicate EMS is teratogenic, mutagenic and carcinogenic; however, no data from humans exist.

FDA has asked Pfizer to implement new specifications to limit the presence of EMS in Pfizer-manufactured Viracept products marked in the United States.

For pediatric patients who are stable on Viracept-containing regimens, FDA and Pfizer agree that the benefit-risk ratio remains favorable and those patients may continue to receive Viracept.

Pediatric patients who need to begin HIV treatment should not start regimens containing Viracept until further notice.

Pregnant women who need to begin antiretroviral therapy should not be offered regimens containing Viracept until further notice.

As a precautionary measure, pregnant women currently receiving Viracept should be switched to an alternative antiretroviral therapy while Pfizer and FDA work to implement the long term EMS specification for Viracept.

For pregnant women with no alternative treatment options, FDA and Pfizer agree that the risk-benefit ratio remains favorable for the continued use of Viracept.

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