5-Amino-1,3,4-thiadiazole-2-thiol is a thiadiazole derivative with antibacterial activity used in the preparation of herbicides as well as carbonic anhydrase inhibitors.

Thiouracil or 2-thiouracil was introduced in 1943 as the first thionamide anti-thyroid drug. Owing to a high frequency of adverse reactions, especially agranulocytosis, use of thiouracil was abandoned in favor of other, less toxic drugs. Thiouracil is not currently used as a thyrostatic drug in humans. Thiouracil inhibits thyroid activity by blocking the enzyme thyroid peroxidase. It is also it is a highly selective inhibitor of neuronal nitric oxide synthase, by interfering with the substrate- and tetrahydrobiopterin (BH(4))-binding to the enzyme. Due to its ability selectively accumulating in de novo-synthesized melanin in overactive melanin-producing cells and thus providing a means to localize melanoma cells, thiouracil can represent a useful new tool to identify modulators of human hair pigmentation.