U.S. regulators plan to ask outside experts to re-evaluate the use of Amgen Inc and Johnson & Johnson anemia drugs when given to patients with chronic kidney disease.

Food and Drug Administration officials, in an article published in the New England Journal of Medicine on Wednesday, said the agency anticipates convening a public advisory committee meeting in 2010 to reevaluate the use of drugs known as erythropoiesis-stimulating agents (ESAs) in people with chronic kidney disease.

ESAs include Amgen's Aranesp and Epogen and J&J's Procrit.

The drugs came under scrutiny after studies showed high doses could lead to heart complications or death. Strong warnings were added in recent years and sales slumped, but the medicines remain widely used for patients with kidney disease and cancer.

FDA spokeswoman Karen Riley said an important question for the advisory panel would be what level of hemoglobin doctors should try to achieve with the drugs. The medicines raise levels of oxygen-carrying hemoglobin in the blood.

The FDA officials, in the journal article, said optimal hemoglobin targets have never been established for patients with chronic kidney disease.

Beyond lowering hemoglobin targets and reducing doses of ESAs, it is also possible that more frequent hemoglobin monitoring and other dosing changes might improve outcomes for patients, the FDA officials said.

They said clinical trials had raised major concerns regarding the use of ESAs to increase hemoglobin concentrations in chronic kidney disease patients above levels needed to avert blood transfusions.

But the studies do not rule out the possibility, however, that modest increases in the hemoglobin level could be beneficial, they added.

Amgen spokeswoman Emma Hurley said the FDA article highlights areas of incomplete understanding regarding appropriate use of ESAs in chronic kidney disease.

The advisory panel meeting will provide an opportunity to discuss the latest evidence on the benefits and risks of the medicines, she said.

Centocor Ortho Biotech, the J&J unit that sells Procrit, said in a statement the company will continue to work with the FDA to ensure that Procrit prescribing information accurately reflects the known benefits and risks of the product, and will continue to communicate this information in a timely fashion.

Amgen reported third-quarter Aranesp sales of $675 million. Sales of J&J's Procrit and anemia drug Eprex were $542 million in the quarter.