Revenue growth Amgen delivered strong business performance in 2004, achieving significant sales and earnings growth while continuing to maintain robust investment in research and development, new manufacturing facilities and product marketing. In 2004, total revenues reached a record $10.6 billion, a 26 percent increase over 2003.
Total 2004 product sales grew 27 percent over the prior year to $10.0 billion, as we continued to build strong franchises in nephrology, supportive cancer care, and inflammatory disease. Worldwide sales growth in 2004 was principally driven by demand for Aranesp® (darbepoetin alfa), Amgen's latest product for the treatment of anemia associated with chronic kidney disease and chemotherapy-induced anemia; ENBREL® (etanercept), Amgen's leading inflammation biologic used in the treatment of diseases such as rheumatoid arthritis, psoriatic arthritis and psoriasis; and Neulasta® (pegfilgrastim), Amgen's once-per-cycle product for decreasing the incidence of neutropenic infections associated with many types of cancer chemotherapy treatments. U.S. sales for Aranesp® and Neulasta® were impacted by higher incentives earned by customers under performance-based contracts.
U.S. product sales increased 22 percent to $8.3 billion, representing 83 percent of Amgen's total product sales in 2004. Amgen's international product sales increased 54 percent to $1.7 billion in 2004. International product sales growth during 2004 benefited by $164 million from foreign currency rate changes. Our international growth was driven primarily by additional market penetration of our products in Europe.
Total sales of EPOGEN® (Epoetin alfa), Amgen's anemia therapy for patients with chronic renal failure on dialysis, increased 7 percent to $2.6 billion. EPOGEN® continued to have solid sales growth after 15 years on the market. This sales growth was primarily driven by demand, which reflects dialysis patient population growth and a continued focus in the renal community on patient outcomes and, to a lesser extent, by increases in wholesaler inventory levels.
Worldwide sales of Aranesp® increased 60 percent in 2004 to $2.5 billion, driven by demand, which benefited from market share gains in both oncology and nephrology and market growth. U.S. sales growth was impacted by higher incentives earned by customers attaining higher sales volumes and growth under performance-based contracts.
Total combined worldwide sales of Neulasta® and NEUPOGEN® (Filgrastim), Amgen's products used to decrease the incidence of many types of chemotherapy-related infections, increased 16 percent in 2004 to $2.9 billion. Combined sales growth for Neulasta® and NEUPOGEN® was driven by worldwide demand for Neulasta®. Worldwide sales of Neulasta® increased 39 percent in 2004 primarily driven by demand, which benefited from new clinical data demonstrating the value of first-cycle use. U.S. sales growth was impacted by higher incentives earned by customers attaining higher sales volumes and growth under performance-based contracts. The decrease in worldwide NEUPOGEN® sales was primarily due to a decline in demand, which reflects the conversion of NEUPOGEN® patients to Neulasta®.
