Chelating/blocking agents for

TABLE 11-50. CHELATING AND BLOCKING AGENTS FOR SELECTED RADIATION EXPOSURES ... 

For patients who are unable to tolerate penicillamine, trientine, another chelating agent, may be used in a daily dose of 1-1.5 g. Trientine appears to have few adverse effects other than mild anemia due to iron deficiency in a few patients. Zinc acetate administered orally increases the fecal excretion of copper and is sometimes used for maintenance therapy. The dose is 50 mg three times a day. Zinc sulfate (200 mg/d orally) has also been used to decrease copper absorption. Zinc blocks copper absorption from the gastrointestinal tract by induction of intestinal cell metallothionein. Its main advantage is its low toxicity compared with that of other anticopper agents, although it may cause gastric irritation when introduced. 

Allyl chloride is used to make intermediates for downstream derivatives such as resins and polymers. Approximately 90% of allyl chloride production is used to synthesize epichlorohydrin, which is used as a basic building block for epoxy resins and in glycerol synthesis. Allyl chloride is also a starting material for allyl ethers of phenols, bisphenol A and phenolic resins, and for some allyl esters. Other compounds made from allyl chloride are quaternary amines used in chelating agents and quaternary ammonium salts, which are used in water clarification and sewage sludge flocculation (Kneupper Saathoff, 1993). 

A wide range of iron chelators have been shown to inhibit ribonucleotide reductase [144-146] and this is likely to be the explanation of the cytotoxic properties of such molecules. Some iron chelators may also function as free radical scavengers. For instance, hydroxyurea appears to inhibit the enzyme by this latter mode of action [144], Such inhibitory agents block the cell division cycle in the S-phase because replication of cellular DNA is arrested. This also suggests possible therapeutic applications. 

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