Rationale for local toxicity of calcium chelators.

Calcium chelating agents, such as ethylenediaminetetraacetate are toxic to urothelium. Their capacity to form complexes with calcium ions, which is the basis for their chemolytical effectiveness, also determines their toxicity. A decrease of chemolytical effectiveness by prior saturation of the chelator with Ca2+ or by lowering the pH to levels unfavourable for calcium binding significantly diminishes tissue injury. Exchange of Mg2+ ions does not, however, diminish tissue damage. The clinical use of calcium ligands is therefore unsafe.