Thalidomide is primarily used in the treatment of multiple myeloma, a type of blood cancer, often in combination with other medications like dexamethasone. It works by inhibiting the growth of cancer cells and reducing the formation of new blood vessels that tumors need to grow. Additionally, it is employed in managing erythema nodosum leprosum, a painful skin condition associated with leprosy, by modulating the immune response and reducing inflammation. Thalidomide’s immunomodulatory and anti-angiogenic properties make it a valuable therapeutic agent in these specific medical conditions. However, its use is strictly regulated due to its potential teratogenic effects, which can cause severe birth defects.