How is latent syphilis treated?

For the purpose of treatment, the Centers for Disease Control and Prevention defines infections of <1 year as early latent syphilis and infections of >1 year as late latent. The World Health Organization considers early latent syphilis to extend up to 2 years.

Like primary and secondary syphilis, early latent syphilis is treated with 2.4 million units (mu) of benzathine penicillin G intramuscularly in a single dose. Late latent syphilis or latent syphilis of unknown duration is treated with a total of 7.2 mu of benzathine penicillin G administered as three doses of 2.4 mu intramuscularly at 1-week intervals. Penicillin-allergic patients are treated with doxycycline or tetracycline for 2 weeks in early latent syphilis and for 4 weeks in late latent syphilis.