General: After intramuscular injection, iron dextran is absorbed from the injection site into the capillaries and the lymphatic system. Circulating iron dextran is removed from the plasma by cells of the reticuloendothelial system, which split the complex into its components of iron and dextran. The iron is immediately bound to the available protein moieties to form hemosiderin or ferritin, the physiological forms of iron, or to a lesser extent to transferrin. This iron which is subject to physiological control replenishes hemoglobin and depleted iron stores.
Dextran, a polyglucose, is either metabolized or excreted. Negligible amounts of iron are lost via the urinary or alimentary pathways after administration of iron dextran.
The major portion of intramuscular injections of iron dextran is absorbed within 72 hours; most of the remaining iron is absorbed over the ensuing 3 to 4 weeks.
Various studies involving intravenously administered 59Fe iron dextran to iron deficient subjects, some of whom had coexisting diseases, have yielded half-life values ranging from 5 hours to more than 20 hours. The 5-hour value was determined for 59Fe iron dextran from a study that used laboratory methods to separate the circulating 59Fe iron dextran from the transferrin-bound 59Fe. The 20-hour value reflects a half-life determined by measuring total 59Fe, both circulating and bound. It should be understood that these half-life values do not represent clearance of iron from the body. Iron is not easily eliminated from the body and accumulation of iron can be toxic.
In vitro studies have shown that removal of iron dextran by dialysis is negligible.1,2 Six different dialyzer membranes were investigated (polysulfone, cuprophane, cellulose acetate, cellulose triacetate, polymethylmethacrylate and polyacrylonitrile), including those considered high efficiency and high flux.