Federal regulators may recommend later this week that doctors prescribe lower doses of a class of popular and lucrative anemia drugs sold by Amgen Inc. and Johnson & Johnson.
Authorities also may request that the companies conduct further safety studies on the medications.
If the recommendations are carried out, it could result in yet another blow to sales of the drugs, taken by more than a million people in the U.S. each year.
Sales of the treatments, sold under the brand names Epogen and Aranesp by Amgen and Procrit by Johnson & Johnson, already have slowed amid recent questions about their safety when used in certain dosages and patients.
A panel of cancer experts, convened by the Food and Drug Administration, is scheduled to meet in Silver Spring, Md., on Thursday. They will assess whether the drugs, known under the general name erythropoietin, are safe at current recommended levels.
In documents on its website Tuesday, the FDA said further restrictions on recommended dosages "may be appropriate to minimize risks to patients."
Although it's possible the committee may choose to do nothing, several analysts believe that the agency's comments suggest it's likely to act.
"There are more questions than answers right now," said Eric Schmidt, an analyst with Cowen & Co. "But if I'm reading the tea leaves, I would say the companies shouldn't be waiting for positive news."
In a statement, Amgen said: "We look forward to discussing with the panel our anemia medicines and their appropriate use with oncology patients."
Erythropoietin drugs are prescribed to cancer and dialysis patients to boost hemoglobin levels. Production of hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the rest of the body, often is impaired in cancer and kidney patients.
Some doctors use higher doses to raise the hemoglobin higher in certain cases, with the hope it will produce better results.
Several recent trials suggest the anemia drugs can raise the risk of heart attack and stroke at such high dosages. Other studies have found they are safe when used in recommended doses and patients.
In March, the FDA added a "black-box warning" to the drugs, advising doctors to prescribe them at their lowest possible doses and only to approved patients.
Although the committee's recommendations would be nonbinding, most physicians follow the agency's guidelines and insurers probably would cut coverage if the drug's label is updated again.
Out of the two manufacturers, Thousand Oaks-based Amgen could be more affected by lower dosage recommendations. The company's anemia drugs accounted for $6.6 billion, or nearly half, of Amgen's revenue in 2006.
Already, sales of the entire class of drugs are expected to fall as much as 20% this year, analysts predict. Schmidt said any further dosing restrictions could cut that by an additional 20%.
Amgen shares fell $1.10, or 1.7%, to $62.66 on Tuesday. Shares of New Brunswick, N.J.-based Johnson & Johnson fell 56 cents, or 0.9%, to $63.70.