Iron pharmacokinetics after administration of ferric-hydroxide-polymaltose complex in rats

This paper reports a study of the pharmacokinetics of ferrous sulphate and ferric-hydroxide-polymaltose complex (Hw 6400, Ferrum Hausmann) administered orally and intravenously to anaemic and non-anaemic rats of both sexes. Radiolabelled ferrous sulphate and ferric-hydroxide-polymaltose complex was used to study iron utilization after oral administration. Measurements of radioactivity in serum, packed red cells, whole blood, liver, kidney, spleen, bone and in some cases in the gastrointestinal tract were made following a range of dosages between 0.84 and 41.9 mg Fe/kg. No significant difference in bioavailability or iron utilization was found between the two iron preparations. Pharmacokinetic measurements following i.v. administration showed different distribution volumes, iron clearance and elimination constants for the two preparations. This difference in pharmacokinetic behaviour following oral administration, particularly in the case of non-anaemic rats, was confirmed by the observation that a 10- to 20 fold smaller dose of FeSO4 than of iron-polymaltose complex was required to achieve the same rise in serum iron. It is therefore not justifiable to draw conclusions about the bioavailability of chemically different iron preparations (iron salts and iron hydroxide complexes) on the basis of AUC values for serum iron increases observed in non-anaemic animals or human subjects.