Copper ion binding and enzyme inhibitory properties of the antithyroid drug methimazole

The antithyroid drug, methimazole (1-methyl-2-thiolimidazole), is a powerful chelator of cupric ion. This is reflected in its ability to selectively inhibit certain copper oxidases. Uricase, ascorbic oxidase and monoamine oxidase are not affected. Ceruloplasmin oxidase is slightly inhibited and tyrosinase is markedly inhibited by methimazole.