In another body blow to Amgen, regulators at Medicare say they have proposed limiting the amount of anemia drugs that it will reimburse for. Amgen reports that sales have already been sliding for anemia drugs and the regulators say that federal reimbursements are likely to drop 10 percent on the new rules. Medicare spends more money on anemia drugs than for any other pharmaceutical. Aranesp and Epogen, marketed by Amgen and J&J, bring in more than $10 billion a year and account for about half of Amgen's sales. That money has built Amgen into the biggest biotech company in the world and funded many of its new development programs.