When did penicillin become an effective treatment for syphilis?

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Scanning electron micrograph of Treponema pallidum, the spirochete bacterium that is the causative agent of syphilis. — syphilis Scanning electron micrograph of *Treponema pallidum*, the spirochete bacterium that is the causative agent of syphilis.

Penicillin became an effective treatment for syphilis in 1943, following the discovery by American physician John Friend Mahoney and his colleagues that the antibiotic could successfully treat nonadvanced cases of the disease.1

Prior to this breakthrough, treatments for syphilis were significantly less effective and often toxic, including the use of mercury and arsenic-based compounds like Salvarsan. The introduction of penicillin revolutionized the management of the infection, leading to a considerable decline in the number of syphilis cases, particularly in developed countries.1