Benzathine Penicillin Dosing for Syphilis

Adult Dosing by Stage

The Centers for Disease Control and Prevention recommends a single dose of 2.4 million units IM for early syphilis 1
For late latent syphilis or unknown duration, the Centers for Disease Control and Prevention recommends a total of 7.2 million units administered as three separate doses of 2.4 million units IM at weekly intervals 2, 1
Each injection must be spaced exactly 7 days apart, with a 10-14 day interval potentially acceptable if a dose is missed 2

For children with acquired syphilis, the Centers for Disease Control and Prevention recommends 50,000 units/kg IM, up to the adult dose of 2.4 million units, for early syphilis as a single dose 1, 4
All children require CSF examination to exclude neurosyphilis before treatment 1, 4

The Centers for Disease Control and Prevention recommends the same single-dose regimen for early syphilis in HIV-infected patients, with additional doses not enhancing efficacy regardless of HIV status 1, 4
For pregnant women, the Centers for Disease Control and Prevention recommends the same stage-appropriate penicillin dosing as non-pregnant adults, with penicillin being the only proven effective treatment to prevent mother-to-fetal transmission 9

For early syphilis, the Centers for Disease Control and Prevention recommends clinical and serologic evaluation at 6 and 12 months 1, 4
A fourfold decline in titer is expected within 6 months for primary/secondary syphilis 3
Treatment failure is defined by titers increasing fourfold after initial decline, or initially high titer failing to decline at least fourfold within 12-24 months 2, 5

The Centers for Disease Control and Prevention advises against using tetracyclines, doxycycline, or erythromycin in pregnant women, as these do not prevent congenital syphilis 9
It is also recommended to avoid comparing titers between different test types, as they are not directly comparable 8