Ceftriaxone is sometimes used as an alternative treatment for syphilis, particularly in patients who cannot receive penicillin. The usual regimen is 1–2 g daily by intramuscular or intravenous injection for 10–14 days. It has shown good activity against Treponema pallidum, especially in early syphilis, though data are more limited compared to benzathine penicillin. Ceftriaxone may be considered in cases of neurosyphilis, ocular syphilis, or penicillin allergy when doxycycline is not suitable. However, because penicillin remains the most reliable option, ceftriaxone is generally viewed as a second-line therapy.