Labels on the anemia drugs Aranesp and Procrit must be changed in a way that could limit their use in treating cancer patients, the U.S. Food and Drug Administration says.

It's the first time the FDA has used its authority under a 2007 law that gave the agency the power to order changes in a drug's prescribing information, The New York Times reported. Before the new law, the FDA could only negotiate with drug makers to change labels.

Amgen makes both Aranesp and Procrit, but Procrit is sold under license by Johnson & Johnson.

In the past year, sales of both drugs fell after studies suggested their use to treat anemia caused by chemotherapy could actually worsen cancer and shorten patients' lives, the Times reported.