FDAnews Drug Daily Bulletin

Pfizer’s protease inhibitor Viracept is no longer recommended as an initial therapy for the treatment of HIV in pediatric patients because the product contains ethyl methane sulfonate (EMS), a genotoxic chemical.

The NIH’s recently updated Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection advise physicians to prescribe Abbott Laboratories’ Kaletra (lopinavir) or Norvir (ritonavir) instead. Roche manufactures Viracept (nelfinavir mesylate) for markets in Europe, and Pfizer makes the drug for use in the U.S.

Pfizer sent “dear doctor” letters last year warning physicians that, while the FDA and Pfizer come up with a new specification for EMS, doctors should not prescribe Viracept unless patients already take it. The impurity results from a chemical reaction when methane sulfonic acid comes into contact with ethanol during the production process for the drug’s active pharmaceutical ingredient.

“When this problem is resolved, nelfinavir will return to being an alternative [protease inhibitor] choice in combination with 2 [nucleoside reverse transcriptase inhibitors] for initial treatment of children [older than] 2 years of age,” the updated guidelines state.