Bioverfügbarkeit des in einem oralen Eisenpräparat enthaltenen Eisen(III)-Hydroxid-Dextrin-Komplexes

Summary

An iron(III)-hydroxide-polymaltose complex used in the FRG for oral iron therapy was labeled with⁵⁹Fe and investigated for bioavailability in subjects with normal and depleted iron stores. Following the oral application of a 100 mg Fe(III)-equivalent of the⁵⁹Fe(III)-hydroxide polymaltose complex the postabsorptive serum increase after 3 h as well as the whole body retention and erythrocyte incorporation of absorbed⁵⁹Fe after 2 weeks were measured by intraindividual comparison with a 100 mg Fe(II)-equivalent in⁵⁹Fe(II)-ascorbate.

Subjects with normal iron stores absorbed and retained in the body 7.95±1.53 (_a±SD) mg Fe from the oral dose from⁵⁹Fe(II)ascorbate but only 0.49±0.42 mg Fe from Fe(III)hydroxide polymaltose. Due to their depleted iron stores subjects in prelatent/latent iron deficiency absorbed and retained increased amounts of 14.6±2.7 mg Fe from⁵⁹Fe(II)ascorbate but only 1.34±0.61 mg Fe from⁵⁹Fe(III)-hydroxide-polymaltose. Because of the existing close correlation (r=0.93) between the whole-body retention and erythrocyte incorporation of absorbed⁵⁹Fe 5.85±1.1 mg Fe from the⁵⁹Fe(II)ascorbate iron and only 0.46±0.45 mg Fe from the⁵⁹Fe(III)-hydroxide polymaltose complex iron were incorporated into erythrocytes by the subjects with normal iron stores after 2 weeks. The erythrocyte-⁵⁹Fe-incorporation was increased to 11.9±2.51 mg Fe from the⁵⁹Fe(II)ascorbate but only 1.42±0.80 mg Fe from the⁵⁹Fe(III)-hydroxide polymaltose iron in subjects with depleted iron stores.

If compared with Fe(II)ascorbate or sulfate (=100%) relative bioavailability values of 10% and 13% respectively, for a polymere iron(III)-citrate complex and 6% and 9%, respectively, for the iron(III)-hydroxide polymaltose complex were estimated for subjects with normal and depleted iron stores. The trivalent iron in the polymaltose complex has the lowest bioavailability of all oral iron preparations investigated with reliable methods up to now and does not represent an exception from the 50-year-old rule that all trivalent iron containing oral iron preparations are so poorly absorbable that they are ineffective in oral iron therapy. As in all other countries, trivalent iron containing oral iron preparations should be climinated from iron therapy also in the FRG.