Background: Equivalence of intravenous (i.v.) and subcutaneous (s.c.) dosage requirements is a notable characteristic of darbepoetin-alpha (DPO), as opposed to other epoetins (EPOs). Currently in Europe, the EPOs/DPO conversion factor (200 IU EPOs = 1 microg DPO) does not take into account the route of drugs administration. To better define this ratio we have conducted a prospective, long-term trial in a group of hemodialysis patients.
Subjects and methods: At the start, we evaluated 40 iron-replete hemodialysis patients, but the final study was performed in the remaining 25 patients. During the first 6 months, patients were on i.v. epoetin-alpha (EPOalpha) maintenance therapy (phase 1: T-6 to T0). After conversion to i.v. DPO (initial 200:1 ratio) the observation was prolonged for a period of 12 months (phase 2: T0 to T12). DPO was administered at extended dose intervals and the EPOalpha/DPO rate was adjusted every month to maintain hemoglobin (Hgb) stability. Iron status and factors inhibiting erythropoiesis were continually checked to exclude unstable patients.
Results: Phase 1: EPOalpha weekly mean dose showed no significant variation. Phase 2: EPOalpha/DPO conversion factor progressively rose from 200 to 256.7 +/- 86.9 IU/microg at T7 (p<0.005) and 336.8 +/- 104.3 IU/microg at T12 (p<0.0005). DPO weekly mean dosage decreased from 40.0 +/- 12.0 microg/week at T0 to 31.6 +/- 3.7 microg/week at T7 (p<0.005) and 24.6 +/- 7.0 microg/week at T12 (p<0.0005). Mean weekly/patient acquisition cost of EPOalpha was euro 70.6 +/- 21.3 (T-6 to T0); after switching, the cost of DPO was euro 72.4 +/- 22.7 (T0) and fell to euro 53.1 +/- 11.2 during T6 to T12.
Conclusions: The progressive increase of EPOalpha/DPO ratio demonstrated that i.v. DPO requires lower doses compared with i.v. EPOalpha. When drugs are administered i.v., the starting EPOalpha/DPO conversion factor should be increased over the 200:1 ratio, similar to recommendations outlined in the United States and Japan. DPO dose reduction translated to notable cost-savings.