What is the recommended treatment regimen for syphilis, including early infection, late latent disease, neurosyphilis, and pregnancy?

Syphilis Treatment

Benzathine penicillin G remains the definitive treatment for all stages of syphilis, with dosing and duration determined by disease stage: single 2.4 million unit IM dose for early infection, three weekly 2.4 million unit IM doses for late latent disease, and IV aqueous penicillin G or ceftriaxone for neurosyphilis. 1

Treatment by Stage

Early Syphilis (Primary, Secondary, and Early Latent <1 year)

• Benzathine penicillin G 2.4 million units IM as a single dose 1
• This applies to patients with documented infection acquired within the preceding year based on:
  • Documented seroconversion
  • Unequivocal symptoms of primary or secondary syphilis
  • Sex partner with confirmed early syphilis

For penicillin-allergic non-pregnant patients: Doxycycline 100 mg orally twice daily for 14 days OR tetracycline 500 mg orally four times daily for 14 days 2, 3

Late Latent Syphilis or Latent Syphilis of Unknown Duration

• Benzathine penicillin G 7.2 million units total: three doses of 2.4 million units IM given at 1-week intervals 1
• Patients who cannot be definitively classified as early latent should be treated as late latent

For penicillin-allergic non-pregnant patients: Doxycycline 100 mg orally twice daily for 28 days OR tetracycline 500 mg orally four times daily for 28 days 1, 3

Critical caveat: If a patient misses a dose during weekly therapy, an interval of 10-14 days between doses may be acceptable before restarting the sequence. However, pregnant patients who miss any dose must repeat the full course of therapy 1

Tertiary Syphilis (Gumma and Cardiovascular)

• Benzathine penicillin G 7.2 million units total: three doses of 2.4 million units IM at 1-week intervals 1
• Note: This does NOT include neurosyphilis, which requires different treatment
• Patients with symptomatic late syphilis should have CSF examination before therapy
• Some experts treat all cardiovascular syphilis with a neurosyphilis regimen 1

Neurosyphilis

Neurosyphilis requires IV therapy and can occur at any stage of syphilis 1

While the provided guidelines reference neurosyphilis treatment, specific regimens are noted to be in separate sections. Based on standard practice and the guideline framework:

• Aqueous crystalline penicillin G 18-24 million units per day (administered as 3-4 million units IV every 4 hours or continuous infusion) for 10-14 days is the standard regimen
• Syphilitic uveitis or other ocular manifestations are treated as neurosyphilis 1

Indications for CSF examination:

• Neurologic or ophthalmic signs/symptoms
• Evidence of active tertiary syphilis (aortitis, gumma, iritis)
• Treatment failure
• HIV infection with late latent syphilis or syphilis of unknown duration 1
• Some specialists recommend CSF examination for all patients with nontreponemal titers >1:32 1

Pregnancy

Pregnant patients MUST receive penicillin regardless of allergy status 1

• Penicillin-allergic pregnant patients should be desensitized and treated with penicillin 1
• No alternative antibiotics are acceptable in pregnancy
• Screening should occur three times: at first prenatal visit, during third trimester, and at delivery 4
• Missed doses are unacceptable—full course must be repeated 1

Pediatric Dosing

Children require CSF examination to exclude neurosyphilis and review of birth/maternal records to distinguish congenital from acquired syphilis 1

Early latent syphilis:

• Benzathine penicillin G 50,000 units/kg IM (up to adult dose of 2.4 million units) as single dose 1

Late latent or unknown duration:

• Benzathine penicillin G 50,000 units/kg IM (up to adult dose of 2.4 million units) given as three doses at 1-week intervals (total 150,000 units/kg up to 7.2 million units) 1

Follow-Up and Treatment Response

Quantitative nontreponemal serologic tests (RPR/VDRL) should be repeated at 6,12, and 24 months 1

Retreatment is indicated if:

• Titers increase fourfold
• Initially high titer (≥1:32) fails to decline at least fourfold within 12-24 months
• Signs or symptoms attributable to syphilis develop 1

Use the same nontreponemal test throughout follow-up for accurate comparison 5

Special Populations and Considerations

HIV-Infected Patients

• Same penicillin regimens as HIV-negative patients 1
• CSF examination recommended for late latent syphilis or syphilis of unknown duration 1
• Efficacy of alternative (non-penicillin) regimens has not been well studied and should be used with caution 1
• More frequent follow-up (3,6,12,24 months) is common practice 5

Key Clinical Pitfalls

1. Do not use macrolides due to potential resistance 5
2. Single-dose ceftriaxone is NOT effective for treating syphilis 6
3. All syphilis patients should be tested for HIV 1
4. Screen all sexual contacts and treat as appropriate 3
5. Recent evidence suggests that for high-titer late latent syphilis (>1:32), single-dose benzathine penicillin G may have similar serological outcomes to three-dose regimens, though this contradicts current guidelines and requires further validation 7