The health care industry spent just over $4 billion on anemia drugs during 2012–2013, with three-quarters of the expenditures going to Amgen Inc. and its Epogen and Aranesp products.

The information was provided by IMS Health in an annual survey of the top 100 drugs used in the United States. The survey looks at total expenditures and the number of prescriptions for each drug.

(Nephrologist survey: Many chronic kidney disease patients might be good candidates for anemia drug Mircera)

Epogen ranked 21st on the list, with sales of $2,214,743,254. Procrit, an anemia drug manufactured by Amgen in the United States but sold by Johnson & Johnson to non-dialysis patients as part of a marketing agreement, tallied $1,047,927.348 in sales and ranked 43rd on the top 100 list. Amgen’s Aranesp ranked 51st in sales at $845.994,421.

Amgen’s Sensipar drug, used for the treatment of secondary hyperparathyroidism, ranked 59th in the survey and tallied $763, 591, 668 in sales.

The annual survey covered October 2012 through September 2013, and drug manufacturers provide sales and prescribing information. The cholesterol-lowering drug rosuvastatin, which goes by the name Crestor and is made by AstraZeneca, was the nation's most prescribed drug during the time period, whereas the antipsychotic aripiprazole, marketed under the name Abilify and manufactured by Otsuka Pharmaceutical, had the highest sales — almost $6.4 billion.