Used historically as an anthelmintic to treat intestinal worm infestations, particularly roundworm and threadworm. It was effective in paralyzing parasites, allowing the host to expel them naturally. Due to its narrow therapeutic window and potential toxicity, including neurotoxic effects and hemolytic anemia, it has been largely replaced by safer synthetic alternatives. Slight use persists in veterinary medicine in specific cases, but overall application is now rare. Also used in research settings for studying parasite physiology and drug mechanisms.