Biotech drug maker Amgen Inc. submitted written testimony prior to a key congressional hearing today in an attempt to head off congressional action that could hamper sales of its most popular anemia drugs.

The House Ways and Means Subcommittee on Health is scheduled to meet to scrutinize how Medicare pays for Amgen’s drug Epogen, which is used to treat anemia in patients on dialysis.

Lawmakers have argued that Medicare’s current payment system creates an incentive for doctors to over-prescribe the drug in order to collect more money from the government.

Concerns arose after studies released earlier this year indicated that higher doses of anemia drugs than the current U.S. Food and Drug Administration-approved label suggests can put patients at an increased risk of stroke, heart attack or death.

Medicare’s No. 1 expense for seniors is anemia treatment. Epogen, along with its sister drug Aranesp, account for 47 percent of Thousand Oaks-based Amgen’s annual sales.

Amgen submitted written testimony before the hearing indicating that doctors have scaled back their use of the drug in recent months and that the majority of use in dialysis has been and continues to be appropriate.

A new analysis of U.S. dialysis data by the company shows that physicians have been using Epogen even more conservatively since the Centers for Medicare & Medicaid Services revised its policy in November 2005, and the FDA made changes to the product labeling last March.

Congressional advisers have suggested Medicare should move to a bundled payment system, in which Epogen payments would be lumped into reimbursement for all other services provided to dialysis clinics. Amgen said that such a system could actually cause doctors to under utilize Epogen and would put dialysis patients at increased risk.

Shares in Amgen were down 8 cents to $55.78 in afternoon trading Tuesday on the Nasdaq.