RESISTANCE TO ERYTHROPOIETIN IN IRON-OVERLOADED HEMODIALYSIS-PATIENTSCAN BE OVERCOME BY ASCORBIC-ACID ADMINISTRATION

Haemodialysis patients with iron overload sometimes develop resistance to erythropoietin therapy due to 'functional iron deficiency'. It is known that this resistance may be overcome by iron supplementation; ho wever, the latter could worsen haemosiderosis. Therefore, we treated f our iron-overloaded haemodialysis patients who had developed relative resistance to erythropoietin (among whom three had features of 'functi onal iron deficiency') with ascorbic acid (500 mg intravenously after haemodialysis, 1-3 times a week). The erythropoietin doses were volunt arily kept unchanged during the study. After a latency of 2-4 weeks, h aematocrit and haemoglobin had increased respectively from 26.5+/-0.7 to 32.7+/-0.4 vol% and from 8.8+/-0.3 to 10.8+/-0.2 g/dl (means+/-SEM, P<0.001). While serum ferritin remained unchanged, transferrin satura tion increased from 27+/-7 to 54+/-12% (P<0.05), suggesting that ascor bic acid supplementation had allowed mobilization of iron from tissue burdens. In one patient, haematocrit declined after withdrawal of vita min C and increased again after rechallenge. Also, ascorbate supplemen tation was continued after the study in two patients and allowed the e rythropoietin doses to be decreased, 8 and 11 weeks, respectively, aft er the start of the trial. When a control group of seven patients with normal iron status and without resistance to erythropoietin were chal lenged in the same manner with ascorbate, no elevation of haematocrit or transferrin saturation was noted. We conclude that ascorbate supple mentation may circumvent resistance to erythropoietin that sometimes o ccurs in iron-overloaded patients, in particular, in the setting of 'f unctional iron deficiency'.