Oral iron absorption test in patients on CAPD: comparison of ferrous sulfate and a polysaccharide ferric complex

We prospectively compared the absorption of ferrous sulfate to that of a polysaccharide ferric complex (Niferex) in 5 healthy controls and 7 stable patients on continuous ambulatory peritoneal dialysis (CAPD). All study subjects received an equivalent of 150 mg of elemental iron of either preparation, in a random fashion. After a baseline fasting serum iron level was obtained, the serum iron concentration was measured at 2 h in the control group and at 2 and 4 h in the CAPD patients. One to 2 months later, all study subjects received the alternative iron compound and were studied in an identical manner. A significant rise in serum iron was only observed in the healthy subjects after the ingestion of ferrous sulfate and not Niferex (ferrous sulfate 102 +/- (SE) 9 vs. 142 +/- 7 Mg/dl, p = 0.0005; Niferex 96 +/- (SE) 10 vs. 102 +/- 12 mg/dl; baseline vs. 2 h, respectively). The absorption of both compounds was poor in the patients on CAPD, with the 2- and 4-hour serum iron levels not significantly higher than the baseline values (ferrous sulfate 73 +/- 7 vs. 107 +/- 21 vs. 109 +/- 21 mg/dl, p = NS; Niferex 57 +/- 11 vs. 65 +/- 14 vs. 60 +/- 11 mg/dl, p = NS; baseline vs. 2 vs. 4 h, respectively). Our data suggest that the absorption of both ferrous sulfate and ferric polysaccharide complex is poor in patients on CAPD.