Arsphenamine is an organic compound that was historically used as a treatment for syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum. Discovered in the early 20th century, it was one of the first effective drugs for this disease and marked a significant advancement in medical treatment. The compound contains arsenic, which is why it is also known as Salvarsan. Although it was groundbreaking at the time, its use declined with the development of safer and more effective antibiotics, such as penicillin, which became the standard treatment for syphilis in the mid-20th century.