Atoxyl, also known as sodium arsanilate or p-aminobenzenearsonic acid sodium salt (C₆H₇AsNNaO₃), is an organoarsenic compound historically significant in medicine. Developed in the early 20th century, it was one of the first synthetic drugs used to treat trypanosomiasis (African sleeping sickness), caused by parasitic protozoa of the genus Trypanosoma. Administered intravenously or intramuscularly, it targeted and eliminated parasites in the bloodstream. It was also explored for treating syphilis, a bacterial infection caused by Treponema pallidum, prior to the advent of penicillin. However, due to its high toxicity, including risks of blindness and neurological damage, its use was discontinued in favor of safer alternatives like organic arsenicals (e.g., Salvarsan). Despite these limitations, Atoxyl played a pivotal role in the pioneering of arsenic-based chemotherapy and advanced the understanding of targeted antimicrobial therapies. Today, it is primarily of historical and research interest as a specialty chemical in pharmaceutical and biochemical studies.