Chelating agents iron excess

Fig. 8. Mechanism proposed for the transfer of iron from low molecular weight chelates to apotransferrin involving the intermediate ternary complex of protein-iron-chelate. The polynuclear iron must be depolymerized prior to its binding by the protein. The presence of excess chelating agents, particularly citrate, leads to the formation of the bis complex which reacts rapidly...

As we have seen, the body has essentially no means of eliminating iron, so an excessive intake of iron causes various problems known as siderosis. Chelating agents are used to treat the excessive buildup of iron. In many cases (he chelates resemble or are identical to the analogous compounds used by bacteria to chelate iron. Thus desferrioxamine B is the drug of choice for African siderosis.1)7 The ideal chelating... 

Excess transition metals can be removed by chelation therapy using chelating agents such as deferoxamine, EDTA or D-penicillamine, and supplements can be used in cases of deficiency (e.g. iron(II) suphate or zinc(II) sulfate). 

Excess iron can be removed by either phlebotomy (letting of blood from a vein) or administration of the chelating agent, deferrioxamine, for cases of chronic excess iron. Ascorbic acid can accelerate iron excretion about twofold. 

Desferoxamine (Desferal) is a chelating agent used to remove excess iron from the body in conditions such as hemochromatosis and in acute iron poisoning. Erythema, probably mediated through histamine release and two cases of urticaria have been described after intramuscular injection (Westlin 1971). After oral treatment no allergic side effects are reported. 

Assessment of the toxicity of a chelator should in principle be done in an adequate model of the target population of iron-loaded patients. Observations with subjects that lack excessive iron stores may be based on unrealistic concentrations of the uncomplexed chelator, or alternatively show effects of removal of needed baseline iron stores. For example, it is not yet clear whether toxic effects of the hydroxypyridones are an inherent property of the agents themselves, a result of chelation of iron or other trace elements at strategic cellular locations, or a consequence of the mobilization of iron in toxic form. Toxicity of these compounds in animal studies has not been observed to the same extent in significant experience with patients... 

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