The treatment of choice for syphilis is which of the following?

• A. Benzathine penicillin G
• B. Valacyclovir
• C. Metronidazole
• D. Ceftriaxone

Answer: (A)

Benzathine penicillin G is the go-to treatment for syphilis because it delivers a prolonged, treponemicidal level of penicillin in the bloodstream with a single injection for early disease (and a course of injections for later stages), ensuring sustained exposure of Treponema pallidum to the antibiotic. This long-acting formulation is specifically effective against the organism and has stood the test of time as the first-line therapy across stages of syphilis, except for neurosyphilis, which requires IV penicillin. The other drugs listed don’t reliably treat syphilis—valacyclovir targets herpesviruses, metronidazole targets anaerobes and certain parasites, and ceftriaxone can be used as an alternative in some penicillin-allergic cases but is not the preferred first-line option.