The letters have requested that both companies detail to Congress exactly how they market their anemia drugs and if there are any financial incentives (kickbacks) paid to physicians to prescribe them.
![anemia](/images/anemia-blood.jpg)
According to IMS health, the three products combined had U.S. sales of $10 billion in 2006. From those sales, $700 million in annual sales of the drugs are estimated to come from "off label" uses, i.e. not FDA approved.
On March 9, 2007 the FDA announced new "black box" warning labels for the drugs, citing an increased risk of blood clots, heart attacks and even death in kidney patients when the drugs are taken at higher than recommended doses. When used in cancer patients with anemia not caused by chemotherapy - a use not approved by FDA - studies showed increased risk of death even when the drugs were prescribed at normal levels.
These three drugs are erythropoiesis stimulating agents (ESAs) and were approved by the FDA to treat anemia in patients with chronic kidney failure and in patients with cancer whose anemia is caused by chemotherapy. Anemia is a blood disorder caused by a shortage of healthy red blood cells.