FDA Warns Of Possible Carcinogen In Antiretroviral Treatment Viracept

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Antiretroviral Drug Viracept

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Tests have detected a "potential human carcinogen" in batches of Pfizer's antiretroviral drug Viracept, FDA and the pharmaceutical company announced Monday, Reutersreports. Pfizer in a letter to health care professionals said that thechemical ethyl methanesulfonate -- or EMS, which is formed duringmanufacturing -- has been shown to cause cancer and birth defects inanimals but that no data from humans are available (Richwine, Reuters, 9/10).

Thecompany advised health care professionals that children who are stableon antiretroviral regimens containing Viracept can remain on the drug,adding that those who need to initiate therapy should not startregimens with Viracept until further notice. The company also said thatpregnant women should refrain from starting regimens with Viracept andthat those currently receiving it should switch to another drug (AP/Yahoo! News,9/10). For pregnant women with no alternative treatment options, "FDAand Pfizer agree that the risk-benefit ration remains favorable for thecontinued use of Viracept," the letter said (Reuters, 9/10).

Pfizer said it is working with FDA to implement immediate and long-term processes to keep EMS levels low (AP/Yahoo! News, 9/10). According to the company, EMS levels are "substantially lower" than those that prompted Roche in June to recall all batches of Viracept in Europe and other countries, Reutersreports. "Pfizer is working with the FDA to prospectively limit EMSlevels in Viracept while still considering the immediate needs ofpatients on therapy," the company said in a statement. Pfizer in theletter said manufacturing changes will reduce EMS levels so thetheoretical increased cancer risk for adults over a person's lifetimewould be less than one case per 100,000 people exposed (Reuters, 9/10).

Reprinted with permission from kaisernetwork.org. You can view theentire Kaiser DailyHIV/AIDS Report, search the archives, and sign up for email delivery at kaisernetwork.org/email . TheKaiser Daily HIV/AIDS Report is published for kaisernetwork.org, a free service ofThe Henry J. Kaiser Family Foundation.

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