Pediatric Syphilis Medication

Updated: Dec 12, 2022
  • Author: Muhammad Waseem, MBBS, MS, FAAP, FACEP, FAHA; Chief Editor: Russell W Steele, MD  more...
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Medication Summary

Treponema pallidum is extremely sensitive to penicillin. Primary, secondary, and early latent syphilis are treated with a single IM dose of penicillin G benzathine (50,000 U/kg; not to exceed 2.4 million U). Nonpregnant patients who are allergic to penicillin and have no evidence of neurosyphilis can be treated with either doxycycline or tetracycline.

Incubating syphilis can also be managed with penicillin. Spectinomycin is ineffective for incubating syphilis.

Current recommendations for management of congenital syphilis include administration of IV penicillin G aqueous and IM penicillin G procaine for 10-14 days. Either penicillin regimen is considered adequate to manage congenital syphilis.



Class Summary

Penicillins are the drug of choice to treat all stages of syphilis. In patients with primary syphilis, doxycycline and tetracycline have shown a high serological treatment success rate, comparable to penicillin. [17]

Penicillin G benzathine (Bicillin L-A)

Primary, secondary, and early latent diseases are treated with a single intramuscular (IM) dose of benzathine penicillin G (50,000 U/kg; not to exceed 2.4 million U). It interferes with the synthesis of cell wall mucopeptides during active multiplication, which results in bactericidal activity. It is a spirocheticide with in vivo activity against T pallidum. It also interferes with cell wall mucopeptide synthesis during replication.

Penicillin G procaine

Treat congenital infection, either proven or presumed, with 10-14 days of aqueous penicillin G or procaine penicillin G. Procaine penicillin G (50,000 U/kg IM) has been recommended as an alternative to treat congenital syphilis, but adequate cerebrospinal fluid (CSF) concentration may not be consistently achieved.

Penicillin G (Pfizerpen)

Penicillin interferes with the synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Aqueous crystalline penicillin G is recommended if congenital syphilis is proved or is highly suspected. The dosage should be based on chronologic, not gestational, age.

Doxycycline (Vibra-Tabs, Vibramycin, Doryx)

Doxycycline is a broad-spectrum, synthetically derived bacteriostatic antibiotic in the tetracycline class. It is almost completely absorbed, concentrates in bile, and is excreted in urine and feces as a biologically active metabolite in high concentrations. It inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. It may block dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.


Tetracycline is an alternative therapy for syphilis infection. It inhibits bacterial growth by binding to the 30S ribosomal unit, preventing protein synthesis.


Probenecid inhibits tubular secretion of penicillin, and it usually increases penicillin plasma levels by any route the antibiotic is administered. A 2- to 4-fold elevation has been demonstrated for various penicillins. It is used as an adjunct to penicillin in late latent and neurosyphilis.