Warning labels on biologic drugs used to treat anemia have been strengthened to reflect concerns that excessive use can boost the risk of heart attacks, stroke and death in cancer and kidney disease patients, it was announced on Nov. 8th.

The new boxed warning label, the most serious a drug can carry, emphasizes that cancer patients have an increased risk of death and showed accelerated tumor growth when treated with elevated doses of Amgen's Epogen and Aranesp or Johnson & Johnson's Procrit.

The companies also strengthened a label warning that using the drugs in higher doses can increase risk of heart attack, stroke, and death in kidney failure patients, and does not improve symptoms of anemia, quality of life, fatigue or patient well-being.

The Food and Drug Administration said it still is not clear whether patients face the same risks when using normal doses of the drugs. The companies hope to answer that question through additional studies.

Millions of cancer and kidney disease patients take the biologic drugs, which have seen sharply reduced use since a study showed increased risk of death in cancer patients whose anemia was not caused by chemotherapy. Concerns also have been expressed over excessive use of the drugs in dialysis patients.

The FDA said the labeling changes reflect new data on potential adverse effects.

"Today's labeling changes are being made to make clear recommendations about the safe and effective use of these products and to strengthen the information about the risks that these drugs pose to patients with cancer and to patients with chronic kidney failure," said Dr. Richard Pazdur, the FDA's director of the Office of Oncology Drug Products.

"We are emphasizing that [these biologics] should be used at the lowest dose necessary to avoid blood transfusions, since that is the only identifiable benefit," said Dr. John Jenkins, director of the FDA's Office of New Drugs. "Doctors should have discussions with their patients about whether to use [them] at all."