It is used mainly as chelating agent in heavy metal poisoning as in lead, mercury and copper poisoning. It is used in Wilson's disease. It ?is used in pharmacy as chelating agent and as immunosuppressant for treating rheumatoid arthritis by reducing the number of T cells, inhibiting the macrophages, by reducing the activity of "Interleukin 1 and rheumatoid factor and in preventing crosslinking of the collagen. It acts as an exogenous NOS modulator.