Warning Issued on Nelfinavir (Viraceprt) for Children and Pregnant Women

NEW YORK, Sept. 10 -- In the wake of a recall in Europe of nelfinavir (Viracept) because of a potentially carcinogenic impurity, Pfizer has issued new guidelines for the anti-retroviral drug's use in the U.S., the FDA reported.

In a Dear Health Professional letter, the company said:

• Pediatric patients who need to begin anti-retroviral therapy for HIV should not be given nelfinavir until further notice, although those currently on a stable regimen including the drug can stay on it.
• Pregnant women who need anti-retroviral therapy shouldn't be given nelfinavir and those already on the drug should be switched off it, unless no alternative exists.

The drug's European recall was sparked when Roche, which markets nelfinavir outside the U.S. and Canada, found excess levels of ethyl methanesulfonate in some batches.

The FDA asked Pfizer to test its product for the impurity, which in animal studies has been shown to be teratogenic, mutagenic and carcinogenic, although no human data exist.

Pfizer said its tests showed levels of ethyl methanesulfonate that were substantially lower than in the European drug and testing continues while the company and the FDA work out long-term guidelines for its use.

The impurity arises during the manufacturing process.

The company added that clinicians should note that many anti-HIV drugs are carcinogenic in animals and that some are mutagenic and teratogenic.