Effects of erythropoietin therapy on iron absorption in chronic renal failure

The effect of erythropoietin administration on the absorption of dietary an d therapeutic iron was examined in patients with anemia of chronic renal fa ilure on maintenance hemodialysis. Absorption from test meals tagged extrin sically with iron 55, iron 59, or both was determined 2 weeks later by usin g incorporated red blood cell radioactivity and whole body counting. In an initial study of food iron absorption, the effect of initiating erythropoie tin therapy was determined by measuring the absorption of heme and nonheme iron before and 2 weeks after the administration of 64 U/kg body weight ery thropoietin (range, 46-85 U/kg body weight) three times weekly. Absorption of heme iron increased 1.6-fold from 18.6% to 30.1% (P < .05), and nonheme iron increased 3.7-fold from 1.3% to 4.9% (P < .01) after erythro-poietin t herapy. In a second study therapeutic iron absorption was evaluated at base line and after erythropoietin administration (63 U/kg body weight (range, 4 8-74 U/kg body weight) three times weekly). The absorption of 50 mg of iron as ferrous sulfate increased 2.4-fold from 3.8% to 9.4% (P < .05) when giv en without food and 4.2-fold from 1.4% to 5.9% (P < .05) when given with fo od after erythropoietin administration. After adjusting for changes in iron stores with serum ferritin after erythropoietin therapy, the enhanced eryt hropoiesis associated with erythropoietin therapy increased absorption abou t S-fold, which was similar to the response observed previously in normal s ubjects. In a final study we examined the absorption of therapeutic iron du ring the steadystate phase of erythropoietin therapy after an erythroid res ponse to erythropoietin had occurred. The absorption of 50 mg of iron was l ower than that occurring with the initiation of erythropoietin therapy at 2 .2% when given alone and 1.3% when taken with food. We conclude that iron a bsorption with or without erythropoietin stimulation is unimpaired in patie nts with chronic renal failure.