Influence of a liquid antacid on the absorption of different iron salts

The influence of a liquid antacid on the absorption of iron from iron tablets was studied in healthy volunteers using a serum iron technique. Tablets containing ferrous salts (carbonate, fumarate, sulphate) with different in-vitro dissolution properties were studied. Co-administration of the antacid and the iron tablets resulted in a marked reduction of the absorption of iron from all preparations studied. The lowest absorption was found when ferrous carbonate was given with the antacid. This was ascribed to the fact that ferrous carbonate is almost completely insoluble at pH-levels near neutral. This was confirmed in a series of patients with achlorhydria in which the absorption from ferrous carbonate was virtually nil. It was concluded that iron tablets and antacid preparations should not be administered at the same time and that ferrous carbonate tablets should not be used in patients with achlorhydria.