Chelation therapy is the administration of a drug that removes toxic metals from the bloodstream. Physicians have used chelation therapy since the 1950s to treat heavy metal poisoning--primarily lead poisoning--and to remove metals that have built up in tissues as a result of such genetic disorders as Wilson's disease, cystinuria, and hemochromatosis.

In addition to these accepted uses, chelation therapy has also been promoted by some as a non-surgical alternative for the treatment of atherosclerosis. However, no controlled scientific study has yet supported these claims and most physicians do not recommend chelation therapy for this purpose.

Chelation therapy is generally only recommmended when high levels of metal are present in the blood, since it does not seem to benefit those with lower levels. Currently, four drugs are used for chelation therapy: edetate calcium disodium (calcium EDTA), dimercaprol (BAL), succimer, and d-Penicillamine. Calcium EDTA is usually injected...