High Quality Content by WIKIPEDIA articles! Levamisole (marketed as the hydrochloride salt under the trade name Ergamisol) is an anthelminthic and immunomodulator belonging to a class of synthetic imidazothiazole derivatives. It was discovered at Janssen Pharmaceutica in 1966. Levamisole has been used in humans to treat parasitic worm infections, and has been studied in combination with other forms of chemotherapy for colon cancer, melanoma, and head and neck cancer. The drug was withdrawn from the U.S. and Canadian markets in 2000 and 2003 respectively, due to the risk of serious side effects and the availability of more effective replacement medications. The key side toxic effect of the drug is agranulocytosis, a severe depletion of white blood cells that leaves patients vulnerable to infection.