Salvarsan is an early antibiotic drug developed in 1909 by Paul Ehrlich to treat syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum. It was the first effective treatment for this disease and marked a significant advancement in medical science. The compound, also known as arsphenamine, contains arsenic and works by targeting the bacteria responsible for syphilis. Although it was groundbreaking at the time, Salvarsan had side effects and was eventually replaced by safer and more effective antibiotics, such as penicillin, in the mid-20th century.