Absorption and side-effects after peroral administration of sustained release iron tablets. Ferro-Retard compared with Ferronicum and Duroferon Duretter.

Study I. In 13 iron deficient patients the absorption from 100 mg ferrous sulphate (Ferro-Retard) after 3 and 5 hours was comparable to the absorption from 176 mg ferrous gluconate in rapidly disintegrating tablets (Ferronicum). Study II. (a) The serum iron elevation in 14 blood donors with normal Hb after administration of ferrous sulphate (100 mg Fe2+) in Ferro-Retard or Duroferon Duretter seemed to be equal when tested on the 4th day after donation of 450 ml blood. (b) The iron absorption, measured by the elevation of serum iron 5 and 8 hours after administration of sustained release tablets, proved to be better on the 11th and especially on the 16th day than on the 4th day after donation. Study III (side-effects). In a study on 113 subjects the total number of complaints was unusually high both before and after administration of placebo, rapidly disintegrating and sustained release ferrous sulphate tablets. The selection of participants and other methodological factors have probably been of importance. Hence, comparisons between different studies of side-effects should always be carried out with caution.