The antibiotic era as we know it today started with syphilis. Yes, the face-ravaging, sanity-altering sexually transmitted infection. At the turn of the 19th century, syphilis was endemic and almost incurable. Caused by the spirochete Treponema pallidium, syphilis was usually treated with inorganic mercury salts. But mercury salts treatment had extremely severe and unpleasant side effects and did not usually work very well. Paul Erlich thought there might be a better way. His idea of a “magic bullet” that selectively targets only disease-causing microbes, and not the human housing those microbes, was based on scientists noticing that aniline and other synthetic dyes, which first were produced in the late 1800s, could stain some specific microbes but not others. Paul Ehrlich argued that special chemical compounds could be created which would “be able to exert their full action exclusively on the parasite harbored within the organism.“ This idea of Erlich’s led him to begin a large-scale and systematic screening program (as we would call it today) in 1904 to find a drug against syphilis.
Paul Erlich and his colleagues synthesized hundreds of derivatives of the highly toxic drug Atoxyl and tested them, over and over, in syphilis-infected rabbits. Finally, in 1909 they came across the sixth compound in the 600th series tested, which they numbered 606, which cured syphilis-infected rabbits. Eureka! Further limited trials showed that 606 could possibly work in human patients too. The drug was marketed under the name Salvarsan, was a great success. Soon a less toxic version called Neosalvarsan was invented. The two enjoyed the status of the most frequently prescribed drug (in the Western World) until their replacement by penicillin in the 1940s.
