OBJECTIVES: Studies have reported dose utilization ratios for epoetin alfa (EPO) versus darbepoetin alfa (DARB) ranging from 126:1 (units:mcg) to 400:1. We sought to determine the relative dosages at which EPO and DARB are utilized in clinical practice for Department of Defense (DoD) beneficiaries. METHODS: Study patients included adults newly started on erythropoiesis-stimulating agents (ESAs) from October 1, 2005 to June 30, 2006 with at least 3 consecutive prescriptions for EPO or DARB. Prescription information was obtained from DoD's Prescription Data Transaction Service Data Warehouse. The Military Health System Management Analysis and Reporting Tool was used to identify study patients with primary or secondary ICD-9-CM codes consistent with chronic kidney disease or malignancy. Patients were excluded if they received both EPO and DARB during the study period or had both nephrology and oncology indications for ESA therapy. Dose utilization ratios were calculated by dividing weekly EPO doses by weekly DARB doses (units:mcg). RESULTS: Overall, 914 patients met study criteria (mean age 68 years; 55% female) with 36% receiving ESA therapy for an oncology indication and 34% for a nephrology indication. Patients received a total of 2,366 ESA prescriptions (59% for EPO and 41% for DARB). The median EPO and DARB doses were 25,452 units per week (interquartile range 10,766 - 41,745) and 98 mcg per week (interquartile range 42 - 133), respectively. The median dose utilization ratios for EPO to DARB were 260:1 for all patients, 370:1 for oncology patients, and 243:1 for nephrology patients. Oncology patients received higher ESA doses than nephrology patients (p<0.001, Mann-Whitney U test). CONCLUSION: The dose utilization ratio of EPO to DARB was higher for oncology patients (370:1) compared to nephrology patients (243:1). Significantly higher ESA doses were used for oncology patients compared to nephrology patients.