CDC Guidelines for Syphilis Treatment

Overall Treatment Recommendation

• Benzathine penicillin G is the definitive therapy for all stages of syphilis; the dose and schedule are determined by the stage of infection (definitive recommendation) 1, 2.

Early Syphilis (Primary, Secondary, and Early Latent)

Standard Regimen

• Primary/secondary syphilis – a single intramuscular dose of benzathine penicillin G 2.4 million units is recommended (high‑level evidence) 2, 3.
• Early latent syphilis (< 1 year) – the same single‑dose regimen (2.4 million units IM) is advised (high‑level evidence) 4, 5.

Pediatric Dosing

• Children with acquired primary, secondary, or early latent syphilis receive benzathine penicillin G 50,000 units/kg IM (maximum adult dose of 2.4 million units) as a single dose (expert opinion) 6, 4, 7.

Follow‑up Monitoring

• Clinical and serologic evaluations are recommended at 3, 6, 9, 12, and 24 months after therapy (expert opinion) 1, 2.

Penicillin‑Allergic, Non‑Pregnant Patients

• Preferred alternative: doxycycline 100 mg orally twice daily for 14 days (moderate evidence) 6, 8, 9.
• If doxycycline cannot be used: tetracycline 500 mg orally four times daily for 14 days (expert opinion) 6.
• Azithromycin is not recommended in the United States because of widespread macrolide resistance and documented treatment failures (strong evidence) 1, 8.
• Ceftriaxone 1 g IV/IM daily for 10 days is a reasonable alternative, supported by a randomized trial showing comparable efficacy to benzathine penicillin (moderate evidence) 8, 9.

Pregnancy Considerations (Penicillin Allergy)

• Pregnant patients allergic to penicillin must undergo desensitization and receive penicillin therapy; no alternative regimens are acceptable (strong recommendation) 2, 3, 6.

Late Latent Syphilis or Syphilis of Unknown Duration

Standard Regimen

• Benzathine penicillin G 7.2 million units total, given as three weekly intramuscular doses of 2.4 million units each (high‑level evidence) 2, 4, 5.
• This extended schedule is required because the infection duration is ≥ 1 year or unknown (expert opinion) 4, 5.

Pediatric Dosing

• Children receive benzathine penicillin G 50,000 units/kg IM (up to 2.4 million units per dose) administered weekly for three weeks (expert opinion) 4, 7.

Penicillin‑Allergic, Non‑Pregnant Patients

• Doxycycline 100 mg orally twice daily for 28 days is the only acceptable alternative (moderate evidence) 10, 8, 9.
• If doxycycline is unsuitable, tetracycline 500 mg orally four times daily for 28 days may be used (expert opinion) 10, 9.
• These alternatives require close serologic and clinical follow‑up because efficacy data are limited (expert opinion) 10, 9.
• Ceftriaxone may be considered, but optimal dose and duration are undefined; consultation with an infectious‑disease specialist is advised (expert opinion) 9.

Tertiary Syphilis (Cardiovascular or Gummatous Disease)

• Treatment mirrors late latent disease: benzathine penicillin G 7.2 million units total, administered as three weekly 2.4 million‑unit IM doses (high‑level evidence) 10, 9.
• A cerebrospinal fluid (CSF) examination must be performed before initiating therapy to exclude neurosyphilis (strong recommendation) 1, 10.
• Management should involve an infectious‑disease specialist (expert opinion) 10, 9.
• Some specialists treat all cardiovascular syphilis with a neurosyphilis regimen (expert opinion) 10, 9.

Neurosyphilis (Including Ocular and Otic Involvement)

Preferred Regimen

• Aqueous crystalline penicillin G 18–24 million units per day (3–4 million units IV every 4 hours or continuous infusion) for 10–14 days (high‑level evidence) 1, 10, 9.

Clinical Considerations

• Neurosyphilis can occur at any stage and requires prompt recognition (expert opinion) 10, 3.
• Ocular syphilis (e.g., uveitis) is classified as neurosyphilis and mandates the above regimen (expert opinion) 10, 9.
• Presence of neurologic signs or symptoms (e.g., cognitive changes, cranial nerve palsies, meningitis, hearing loss, stroke) mandates CSF examination before treatment (strong recommendation) 1, 10.

Alternative Regimen (Compliance‑Assured)

• Procaine penicillin G 2.4 million units IM once daily plus probenecid 500 mg orally four times daily for 10–14 days (moderate evidence) 1, 10, 9.
• Probenecid must not be used in patients with sulfa allergy (strong recommendation) 1.
• Some specialists add benzathine penicillin G 2.4 million units IM weekly for up to 3 weeks after completing neurosyphilis therapy to achieve comparable total duration (expert opinion) 1, 10.

Penicillin‑Allergic Patients

• Penicillin desensitization is the preferred approach; no alternative regimens are truly acceptable for neurosyphilis (strong recommendation) 1, 9.
• Ceftriaxone 2 g IV daily for 10–14 days may be considered, but data are limited (moderate evidence) 1, 9.
• Some patients allergic to penicillin may also be allergic to ceftriaxone (expert opinion) 9.

HIV‑Infected Patients

• Early syphilis in HIV‑positive individuals is treated with the same single dose of benzathine penicillin G 2.4 million units IM as in HIV‑negative patients (high‑level evidence) 1, 2, 3, 11.
• Current data show no benefit to multiple benzathine penicillin doses for early syphilis in HIV‑positive patients (moderate evidence) 8.
• Some clinicians recommend three weekly doses for HIV‑positive patients with early syphilis, although benefit remains unproven (expert opinion) 1, 2, 3.
• Enhanced follow‑up is essential: clinical and serologic assessments at 3, 6, 9, 12, and 24 months (expert opinion) 1, 2, 3.
• For late latent syphilis or syphilis of unknown duration, a CSF examination should be performed before treatment (strong recommendation) 2, 3.
• If CSF findings are normal, the recommended regimen is three weekly benzathine penicillin G 2.4 million units IM doses (high‑level evidence) 2, 3.

Critical Pitfalls

• Pregnancy: Alternatives to penicillin must never be used; desensitization is mandatory (strong recommendation) 2, 10, 3, 6.
• Azithromycin: Should not be used for syphilis treatment in the United States because macrolide‑resistant Treponema pallidum strains are prevalent and treatment failures have been documented (strong evidence) 1, 8.

Serologic Response and Follow‑up

• Early syphilis should demonstrate a serologic response by 6 months after treatment (expert opinion).
• Latent syphilis typically requires 12–24 months for an adequate serologic decline (expert opinion).
• A proportion of patients may remain “serofast” (persistently low‑titer positive) despite appropriate therapy; this phenomenon is recognized in recent studies (moderate evidence) 8.

Syphilis Treatment Guidelines (Cited Evidence)

General Treatment Recommendations

• Benzathine penicillin G is the definitive therapy for all stages of syphilis; a single 2.4 million‑unit intramuscular (IM) dose treats early syphilis, while three weekly 2.4 million‑unit IM doses (total 7.2 million units) are required for late latent or tertiary disease【12】【13】.

Early Syphilis (Primary, Secondary, Early Latent ≤ 1 year)

First‑line Regimen

• Administer a single 2.4 million‑unit IM dose of benzathine penicillin G to all patients with early syphilis【12】【13】.

Alternative Regimens for Penicillin‑Allergic, Non‑Pregnant Patients

• Doxycycline 100 mg orally twice daily for 14 days is the preferred alternative【14】.
• Tetracycline 500 mg orally four times daily for 14 days is an acceptable second alternative if doxycycline cannot be used【14】.

Follow‑up Monitoring

• Perform clinical and serologic evaluations at 3, 6, 9, 12, and 24 months after therapy【15】.
• If nontreponemal titers rise fourfold, fail to decline fourfold within 6–12 months, or new symptoms appear, obtain a cerebrospinal fluid (CSF) examination and consider retreatment【12】【14】.

Late Latent Syphilis or Syphilis of Unknown Duration

First‑line Regimen

• Give benzathine penicillin G 7.2 million units total, administered as three weekly 2.4 million‑unit IM injections【12】【13】.

Missed Dose Policy

• Missed doses are unacceptable for pregnant patients; the full three‑dose course must be restarted【12】.

Alternative Regimens for Penicillin‑Allergic, Non‑Pregnant Patients

• Doxycycline 100 mg orally twice daily for 28 days is the only acceptable alternative【14】【16】.
• Tetracycline 500 mg orally four times daily for 28 days may be used if doxycycline is unsuitable【14】【16】.
• These alternatives require close serologic and clinical follow‑up because efficacy data are limited【16】.

Follow‑up Monitoring

• Obtain quantitative nontreponemal serologic tests at 6, 12, and 24 months【12】【14】.
• Perform CSF examination if titers increase fourfold, an initial high titer (≥ 1:32) fails to decline fourfold within 12–24 months, or neurologic/ophthalmic signs develop【12】【16】.

Tertiary Syphilis (Cardiovascular or Gummatous Disease)

• Treat with benzathine penicillin G 7.2 million units total, given as three weekly 2.4 million‑unit IM doses【14】【16】.
• A CSF examination must be performed before initiating therapy to exclude neurosyphilis【16】.
• Management should involve an infectious‑disease specialist【16】.

Syphilis in Pregnancy

• Penicillin is the only acceptable treatment for syphilis in pregnancy; it prevents maternal transmission and treats fetal infection【17】【15】.
• Pregnant patients allergic to penicillin must undergo desensitization and receive penicillin therapy; no alternative regimens are acceptable【17】【13】.
• Use the stage‑appropriate penicillin regimen (single dose for early disease, three weekly doses for late latent)【17】【15】.
• Some experts recommend a second 2.4 million‑unit IM dose one week after the initial dose for primary, secondary, or early latent syphilis in pregnant women【17】.

Screening Recommendations

• All pregnant women should be screened serologically for syphilis early in pregnancy【17】【15】.
• In high‑prevalence populations, screen twice during the third trimester (at 28 weeks and at delivery)【17】.
• Women who deliver a stillborn infant after 20 weeks’ gestation should be tested for syphilis【17】.

Pregnancy‑Specific Risks

• Treatment of syphilis during the second half of pregnancy is associated with an increased risk of premature labor【17】.

Syphilis in HIV‑Infected Patients

Early Syphilis

• Treat HIV‑positive patients with the same single 2.4 million‑unit IM dose of benzathine penicillin G as HIV‑negative patients【15】【18】.
• Some clinicians recommend three weekly doses for HIV‑positive patients with early syphilis, although benefit remains unproven【15】.
• Enhanced follow‑up with clinical and serologic assessments at 3, 6, 9, 12, and 24 months is essential【17】【15】.

Late Latent Syphilis

• Perform a CSF examination before treatment【17】【15】.
• If CSF findings are normal, treat with three weekly 2.4 million‑unit IM doses of benzathine penicillin G【17】【15】.
• If nontreponemal titers do not decrease fourfold within 6–12 months, strongly consider repeat CSF examination and retreatment【17】【15】.

Pediatric Dosing

• Early latent syphilis: benzathine penicillin G 50,000 units/kg IM (maximum 2.4 million units) as a single dose【12】【13】.
• Late latent syphilis: benzathine penicillin G 50,000 units/kg IM weekly for three weeks (total 150,000 units/kg, maximum 7.2 million units)【12】【13】.
• Children should undergo a CSF examination to exclude neurosyphilis before treatment【12】【13】.

Indications for CSF Examination (Across All Populations)

• Presence of neurologic or ophthalmic signs/symptoms【12】【14】【16】.
• Evidence of active tertiary syphilis (e.g., aortitis, gumma, iritis)【12】【14】【16】.
• Suspected treatment failure (e.g., persistent or rising titers)【12】【14】【16】.
• HIV infection with late latent syphilis or syphilis of unknown duration【17】【12】【16】.
• Some specialists recommend CSF examination for any patient with a nontreponemal titer ≥ 1:32, although the risk of neurosyphilis at this level is uncertain【12】.

CDC Guidelines for Syphilis Treatment and Management

Early Syphilis (Primary, Secondary, Early Latent ≤ 1 year)

• Standard therapy: Benzathine penicillin G 2.4 million units given intramuscularly as a single dose. The CDC recommends this regimen for all patients with early syphilis. 19
• Penicillin‑allergic, non‑pregnant adults: Doxycycline 100 mg orally twice daily for 14 days is the preferred alternative. 20
• If doxycycline cannot be used: Tetracycline 500 mg orally four times daily for 14 days is an acceptable substitute. 19
• Alternative parenteral regimen: Ceftriaxone 1 g intravenously or intramuscularly daily for 10 days is a reasonable alternative, supported by a randomized trial showing efficacy comparable to benzathine penicillin. 21
• Azithromycin: Must not be used in the United States because of widespread macrolide‑resistant Treponema pallidum and documented treatment failures. 21

Late Latent Syphilis or Syphilis of Unknown Duration

• Standard therapy: Benzathine penicillin G 7.2 million units total, administered as three weekly intramuscular injections of 2.4 million units each. The CDC specifies this schedule for infections ≥ 1 year or of unknown duration. [19][20]
• Penicillin‑allergic, non‑pregnant adults: Doxycycline 100 mg orally twice daily for 28 days is the only acceptable alternative. [20][22]
• If doxycycline unsuitable: Tetracycline 500 mg orally four times daily for 28 days may be used, but requires close serologic and clinical follow‑up because efficacy data are limited. [19][20]

Pediatric Dosing

• Early disease: Benzathine penicillin G 50,000 units/kg intramuscularly as a single dose (maximum 2.4 million units). 19
• Late latent disease: Same dose (50,000 units/kg) given weekly for three weeks. 19
• CSF examination: Recommended before treatment to exclude neurosyphilis. 19

Missed Dose Policy

• Pregnant patients: Any missed dose requires restarting the full three‑dose benzathine penicillin course. 20
• Non‑pregnant patients: An interval of 10–14 days between doses may be acceptable before restarting the sequence. 20

Tertiary Syphilis (Cardiovascular or Gummatous)

• Treatment: Benzathine penicillin G 7.2 million units total, given as three weekly 2.4 million‑unit IM injections. [20][22]
• CSF examination: Must be performed before initiating therapy to rule out neurosyphilis. [23][22]
• Specialist involvement: Management should involve an infectious‑disease specialist; some experts use a neurosyphilis regimen for all cardiovascular cases. [22][23]

Neurosyphilis (Including Ocular and Otic Involvement)

• Preferred regimen: Aqueous crystalline penicillin G 18–24 million units per day (3–4 million units IV every 4 hours or continuous infusion) for 10–14 days. 23
• Alternative (if compliance assured): Procaine penicillin G 2.4 million units IM once daily plus probenecid 500 mg orally four times daily for 10–14 days. 23
• Ocular syphilis: Classified as neurosyphilis; therefore the neurosyphilis regimen is mandatory. 23
• Neurologic signs (e.g., cranial nerve palsy, meningitis, hearing loss, stroke): Require CSF examination before treatment. 23

Syphilis in Pregnancy

• Penicillin is the only acceptable treatment for syphilis during pregnancy. 19
• Penicillin allergy: Pregnant patients must undergo desensitization and receive penicillin; no alternative regimens are acceptable. [19][20]

Syphilis in HIV‑Infected Patients

• Early syphilis: Treat with the same single 2.4 million‑unit IM dose of benzathine penicillin G as in HIV‑negative patients; multiple doses provide no additional benefit. 21
• Late latent syphilis: Perform a CSF examination before treatment; if CSF findings are normal, treat with three weekly 2.4 million‑unit IM doses of benzathine penicillin G. [20][24]

Indications for CSF Examination (CDC Recommendation)

• Presence of neurologic or ophthalmic signs/symptoms. [19][20]
• Evidence of active tertiary disease (e.g., aortitis, gumma, iritis). [19][20]
• Suspected treatment failure (persistent or rising serologic titers). [19][20]
• HIV infection with late latent syphilis or syphilis of unknown duration. [19][20]
• Some clinicians recommend CSF examination for any patient with a nontreponemal titer ≥ 1:32, although the risk of neurosyphilis at this level is uncertain. 20

Follow‑Up Monitoring

• Early syphilis: Clinical and serologic evaluations at 3, 6, 9, 12, and 24 months after therapy. If titers rise fourfold or fail to decline fourfold within 6–12 months, obtain a CSF examination and consider retreatment. [20][25]
• Late latent syphilis: Quantitative nontreponemal serologic tests at 6, 12, and 24 months; perform CSF examination if titers increase fourfold, an initial high titer (≥ 1:32) fails to decline within 12–24 months, or neurologic/ophthalmic signs develop. [20][22]

Critical Pitfalls

• Pregnancy: Never use non‑penicillin alternatives; desensitization is mandatory. [19][20]
• Azithromycin: Should never be used for syphilis treatment in the United States because of macrolide‑resistant T. pallidum. 21
• Serofast state: Some patients remain persistently low‑titer positive after appropriate therapy; this does not always indicate treatment failure. 21
• HIV testing: All patients diagnosed with syphilis should be screened for HIV infection. [19][23]

Management of Membranous Nephropathy Associated with Syphilis

Antimicrobial Treatment Regimens

• Early syphilis (primary, secondary, or early latent < 1 year) – A single intramuscular dose of benzathine penicillin G 2.4 million U is recommended for all patients, including those with concurrent membranous nephropathy. This regimen is endorsed by the CDC MMWR recommendations. [26] [27]
• Late latent syphilis or infection of unknown duration (≥ 1 year) – Benzathine penicillin G 2.4 million U IM once weekly for three weeks (total 7.2 million U) is required to eradicate the infection. [27] [28]
• Penicillin‑allergic, non‑pregnant adults – early syphilis – Doxycycline 100 mg orally twice daily for 14 days is an accepted alternative. [27] [29]
• Penicillin‑allergic, non‑pregnant adults – early syphilis (if doxycycline contraindicated) – Tetracycline 500 mg orally four times daily for 14 days may be used. 27
• Penicillin‑allergic, non‑pregnant adults – late latent syphilis – Doxycycline 100 mg orally twice daily for 28 days is recommended; tetracycline 500 mg four times daily for 28 days is a second‑line option. Close serologic monitoring is advised because efficacy data are limited. [27] [28]
• Pregnant patients with penicillin allergy – Desensitization and treatment with benzathine penicillin G are mandatory; no alternative regimens are considered acceptable during pregnancy. [26] [27] [29] [30]

Special Populations

HIV‑Infected Patients

• Early syphilis – Treat with the same single‑dose benzathine penicillin G 2.4 million U IM as in HIV‑negative individuals. [31] [28]
• Some experts suggest three weekly doses, although the additional benefit has not been proven. [31] [32]
• Intensified serologic follow‑up at 3, 6, 9, 12, and 24 months is recommended. [28] [32]
• Late latent syphilis – Perform a cerebrospinal fluid (CSF) examination before therapy; if CSF is normal, administer three weekly doses of benzathine penicillin G 2.4 million U IM. [28] [32]

Pediatric Patients

• Early syphilis – Benzathine penicillin G 50,000 U/kg IM as a single dose (maximum 2.4 million U). [26] [27]
• Late latent syphilis – Benzathine penicillin G 50,000 U/kg IM weekly for three weeks (maximum 7.2 million U total). 27
• A CSF examination should be performed before treatment to exclude neurosyphilis. [26] [27]

Follow‑Up and Monitoring

• Early syphilis – Clinical and non‑treponemal serologic testing at 3, 6, 9, 12, and 24 months after therapy. [28] [32]
• Late latent syphilis – Quantitative non‑treponemal tests at 6, 12, and 24 months. 27
• Criteria for additional evaluation – If titers rise four‑fold or fail to decline four‑fold within 6–12 months (early) or 12–24 months (late), a CSF examination and possible retreatment are indicated. [30] [33]

Screening Recommendations

• The KDIGO guideline advises routine screening for syphilis (alongside TB, HBV, HCV, and HIV) in patients with glomerular disease, especially those presenting with nephrotic syndrome. 34

Contraindicated Therapies

• Azithromycin is not recommended for syphilis treatment because of widespread macrolide resistance and documented therapeutic failures. 31

Clinical Evaluation and Risk‑Based Treatment for Discordant Syphilis Serology

Clinical Assessment

• Examine patients for signs of primary (chancre), secondary (rash or mucocutaneous lesions), or tertiary syphilis when a treponemal antibody is positive, the rapid plasma reagin (RPR) is negative, and the TP‑PA result is inconclusive. This recommendation follows the CDC MMWR guidance (1998) 35.

Treatment Indications Based on Risk

• Initiate syphilis treatment in individuals with high‑risk sexual behavior (e.g., men who have sex with men, multiple recent partners, or known exposure to syphilis) when follow‑up cannot be reliably ensured, even if the TP‑PA remains inconclusive. This approach is supported by evidence published in Clinical Infectious Diseases (2022) 36.

CDC Guidelines for Syphilis Treatment and Management

1. Recommended Treatment Regimens

• Early syphilis (primary, secondary, early latent < 1 yr) – penicillin‑allergic, non‑pregnant patients: Doxycycline 100 mg orally twice daily for 14 days is the first‑line alternative; tetracycline 500 mg orally four times daily for 14 days is a second option. [​37]
• Early syphilis – penicillin‑allergic, non‑pregnant patients: A 10‑day course of ceftriaxone 1 g IV or IM daily provides comparable efficacy to benzathine penicillin (supported by a randomized trial). [​37]
• Early syphilis – penicillin‑allergic, non‑pregnant patients: Azithromycin should not be used because of widespread macrolide‑resistant Treponema pallidum and documented treatment failures in the United States. [​37]
• Late latent syphilis or syphilis of unknown duration (≥ 1 yr): Benzathine penicillin G 2.4 million units IM weekly for three consecutive weeks (total 7.2 million units). [​37]
• Late latent syphilis – penicillin‑allergic, non‑pregnant patients: Doxycycline 100 mg orally twice daily for 28 days is the only acceptable alternative; tetracycline 500 mg orally four times daily for 28 days is a second‑line option, though efficacy data are limited. [​37]
• Tertiary syphilis (cardiovascular or gummatous disease): Benzathine penicillin G 7.2 million units total, given as three weekly 2.4 million‑unit IM injections; a CSF examination is mandatory before therapy to exclude neurosyphilis. [​38]
• Neurosyphilis (including ocular and otic disease): Preferred regimen is aqueous crystalline penicillin G 18–24 million units per day (3–4 million units IV every 4 h or continuous infusion) for 10–14 days. [​38][​37]
• Neurosyphilis – alternative when compliance is assured: Procaine penicillin G 2.4 million units IM daily plus probenecid 500 mg orally four times daily for 10–14 days; probenecid must be avoided in patients with sulfa allergy. [​38]
• Neurosyphilis – penicillin‑allergic patients: Penicillin desensitization is the preferred approach; ceftriaxone 2 g IV daily for 10–14 days may be considered, but data are limited and cross‑reactivity is possible. [​37]

2. Follow‑up and Monitoring

• Early syphilis (all patients): Clinical and serologic evaluations at 3, 6, 9, 12, and 24 months; treatment failure is defined by a ≥ 4‑fold rise in nontreponemal titers, failure to achieve a ≥ 4‑fold decline within 6–12 months, or emergence of new symptoms. [​37]
• Late latent syphilis (all patients): Quantitative nontreponemal serologic testing at 6, 12, and 24 months; CSF examination is indicated if titers rise ≥ 4‑fold, high titers (≥ 1:32) fail to decline ≥ 4‑fold within 12–24 months, or neurologic/ophthalmic signs develop. [​37]
• Neurosyphilis: If CSF pleocytosis was present at baseline, repeat lumbar puncture every 6 months until cell count normalizes; consider retreatment if CSF cell count has not decreased after 6 months or remains abnormal after 2 years. [​38]

3. Special Populations

Pregnancy

• Penicillin is the only acceptable treatment for syphilis in pregnancy; allergic patients must undergo desensitization and receive penicillin therapy. [​37][​39]
• Use the stage‑appropriate penicillin regimen (single dose for early disease, three weekly doses for late latent). [​37]
• Some experts recommend a second 2.4 million‑unit IM dose one week after the initial dose for early syphilis in pregnant women. [​39]
• Screening: All pregnant women should be screened serologically at the first prenatal visit; in high‑prevalence settings, repeat screening at 28 weeks and at delivery is advised. [​40]
• Missed dose policy: Any missed benzathine penicillin dose requires restarting the full three‑dose course. [​37]

HIV‑Infected Patients

• Early syphilis is treated with the same single 2.4 million‑unit IM dose of benzathine penicillin as in HIV‑negative patients; multiple doses have not shown benefit. [​37][​40]
• Enhanced follow‑up (clinical and serologic) at 3, 6, 9, 12, and 24 months is essential. [​37][​40]
• Late latent syphilis: Perform a CSF examination before treatment; if CSF is normal, treat with three weekly benzathine penicillin doses. [​37][​39]
• In HIV‑infected patients with CD4 ≤ 350 cells/µL or RPR ≥ 1:32, CSF abnormalities are more likely, but CSF examination without neurologic symptoms has not been shown to improve outcomes. [​37]

Pediatric Patients

• Early syphilis: Benzathine penicillin G 50,000 units/kg IM as a single dose (maximum 2.4 million units). [​37]
• Late latent syphilis: Benzathine penicillin G 50,000 units/kg IM weekly for three weeks (maximum 7.2 million units total). [​37]
• CSF examination should be performed before therapy to exclude neurosyphilis. [​37]

4. Indications for Lumbar Puncture (CSF Examination)

• Neurologic signs or symptoms (e.g., cranial nerve palsies, meningitis, cognitive changes, stroke). [​38][​37]
• Ophthalmic manifestations (uveitis, neuroretinitis, optic neuritis). [​38]
• Auditory symptoms or hearing loss. [​38]
• Evidence of active tertiary disease (aortitis, gumma, iritis). [​38]
• Suspected treatment failure (persistent or rising serologic titers). [​37]
• HIV infection with late latent syphilis or syphilis of unknown duration. [​37][​39]

5. Contraindicated Therapies

• Azithromycin must not be used for syphilis treatment in the United States because of widespread macrolide‑resistant T. pallidum and documented failures. [​37]

6. Expected Serologic Responses

• Early syphilis: A ≥ 4‑fold decline in nontreponemal titers should occur within 6 months after adequate therapy. [​37]
• Late latent syphilis: Adequate serologic decline typically requires 12–24 months; treponemal tests (FTA‑ABS, TP‑PA) often remain positive indefinitely despite successful treatment. [​37]

Guideline Recommendations for Syphilis Management

Diagnostic Recommendations

• Perform cerebrospinal fluid (CSF) examination to rule out neurosyphilis before using any non‑penicillin regimen in patients with late latent syphilis or syphilis of unknown duration who are allergic to penicillin. The CDC (MMWR Recommendations and Reports) emphasizes this prerequisite to ensure appropriate therapy. 41, 42

Treatment Recommendations

• Consider the neurosyphilis treatment regimen (high‑dose intravenous aqueous crystalline penicillin) for all cases of cardiovascular syphilis, as advocated by some experts. This approach aligns with CDC guidance for comprehensive management of severe syphilitic disease. 41

Screening Recommendations

• Test every individual diagnosed with syphilis for HIV infection. The CDC (MMWR Recommendations and Reports) recommends universal HIV screening in this population to identify co‑infection and guide management. 41, 42

Treatment of Primary Syphilis (Chancre)

First‑Line Therapy

• The CDC recommends a single intramuscular dose of benzathine penicillin G 2.4 million units as the definitive treatment for chancre and all forms of early syphilis, achieving cure, preventing sexual transmission, and averting late sequelae【43】【44】【45】.
• This regimen is supported by decades‑long evidence and remains the only FDA‑approved therapy for syphilis【43】【46】【44】.

Mandatory Concurrent Testing

• All patients diagnosed with syphilis should be tested for HIV infection at the time of diagnosis【43】【46】【45】.
• In regions with high HIV prevalence, repeat HIV testing is advised for initially negative patients after 3 months【43】【45】.

Management of Penicillin‑Allergic, Non‑Pregnant Adults

• Doxycycline 100 mg orally twice daily for 14 days is the preferred alternative regimen (moderate‑quality evidence)【47】【48】【49】【46】【50】.
• Doxycycline offers better patient compliance than tetracycline because of fewer gastrointestinal adverse effects【47】【48】.
• If doxycycline cannot be used, tetracycline 500 mg orally four times daily for 14 days is an acceptable substitute【47】【48】【49】【46】.
• Ceftriaxone 1 g IV or IM daily for 10 days is a reasonable alternative; a 2025 randomized controlled trial demonstrated comparable efficacy to benzathine penicillin【50】.

Contraindicated Regimens

• Azithromycin must not be used in the United States for syphilis treatment because of widespread macrolide‑resistant Treponema pallidum and documented failures【47】【48】【50】.

Pregnancy Considerations

• Pregnant patients with penicillin allergy must undergo desensitization and receive penicillin therapy; no alternative agents are acceptable (strong recommendation)【47】【48】【49】【46】.

Pediatric Dosing

• Benzathine penicillin G 50 000 units/kg IM as a single dose (maximum 2.4 million units) is the recommended regimen for children with primary syphilis【43】【45】【46】【44】.
• A cerebrospinal fluid (CSF) examination is mandatory before treatment to exclude neurosyphilis in pediatric patients【43】【45】【44】.
• Child‑protection services should be consulted for all children with acquired syphilis【43】【45】【46】【44】.

Follow‑Up Monitoring

• Clinical and serologic evaluations are required at 3, 6, 9, 12, and 24 months post‑treatment【43】【47】【46】.
• Quantitative nontreponemal tests (RPR or VDRL) should be used to monitor response【43】【46】.
• A ≥4‑fold decline in nontreponemal titers within 6 months indicates adequate therapeutic response【47】【46】.

Indicators of Treatment Failure or Reinfection

• Persistent or recurrent clinical signs/symptoms【43】【46】.
• A sustained ≥4‑fold increase in nontreponemal titer compared with baseline【43】【47】【46】.
• Failure of titers to decline ≥4‑fold within 6 months after therapy【47】【46】.

Management of Treatment Failure

• Re‑evaluate for HIV infection in any patient with inadequate serologic response【47】【46】.
• Perform a CSF examination to rule out occult neurosyphilis【47】【46】.
• If neurosyphilis is excluded, retreat with benzathine penicillin G 2.4 million units IM weekly for 3 weeks【47】【48】【46】.

Neurosyphilis Evaluation

• Neurologic manifestations (meningitis, cognitive changes, cranial nerve palsies, stroke) warrant CSF examination【43】【45】【46】【44】.
• Ophthalmic manifestations (uveitis, neuroretinitis, optic neuritis) also require CSF evaluation【43】【46】.
• Routine lumbar puncture is NOT recommended for uncomplicated primary syphilis, despite frequent CSF invasion by T. pallidum【43】【45】【46】【44】.
• Only a minority of patients develop clinical neurosyphilis after standard therapy【43】【45】【44】.

HIV‑Infected Patients

• Treat HIV‑positive individuals with the same single 2.4 million‑unit IM dose of benzathine penicillin; randomized data show no advantage of multiple doses【50】.
• Enhanced follow‑up at 3, 6, 9, 12, and 24 months is essential because of a higher risk of treatment failure【47】【46】.

Key Pitfalls & Safety Considerations

• Never substitute non‑penicillin agents in pregnant patients; desensitization is mandatory【47】【48】【49】【46】.
• Avoid azithromycin due to documented resistance in the United States【47】【48】【50】.
• Do not interpret persistent low‑titer seropositivity as failure; some patients remain “serofast” despite cure【50】.
• Close follow‑up is required for all non‑penicillin regimens because efficacy data are limited compared with penicillin【47】【48】【50】.

CDC Syphilis Management Guidelines

1. Diagnosis and Initial Evaluation

• All individuals diagnosed with syphilis should be tested for HIV at the time of diagnosis. 51
• Perform a lumbar puncture (CSF examination) when any of the following are present: neurologic signs or symptoms (e.g., cranial nerve palsy, meningitis, cognitive change, stroke); ophthalmic manifestations (e.g., uveitis, neuroretinitis, optic neuritis); auditory symptoms or hearing loss; evidence of active tertiary disease (aortitis, gumma, iritis); suspected treatment failure indicated by persistent or rising serologic titers; or HIV infection with late‑latent syphilis or syphilis of unknown duration. 52, 53, 54, 55

2. Treatment by Stage

2.1 Early Syphilis (Primary, Secondary, Early Latent < 1 yr)

2.2 Late Latent Syphilis / Unknown Duration (≥ 1 yr)

• Benzathine penicillin G – 7.2 million units total, administered as three weekly IM injections of 2.4 million units each. Recommended for all patients (including HIV‑positive) unless contraindicated. 52, 53
• Penicillin‑allergic, non‑pregnant alternatives – Doxycycline 100 mg PO BID for 28 days (preferred) or Tetracycline 500 mg PO QID for 28 days; both require close serologic and clinical follow‑up because efficacy data are limited. 52, 53
• CSF examination must be performed before using any non‑penicillin regimen to exclude neurosyphilis. 56
• In pregnant patients, any missed dose mandates restarting the full three‑dose course. 53

2.3 Tertiary Syphilis (Cardiovascular or Gummatous)

• Benzathine penicillin G – 7.2 million units total (three weekly 2.4 million‑unit IM injections). 52, 53
• CSF examination is mandatory before initiating therapy to rule out neurosyphilis. 52, 53
• Management should involve an infectious‑disease specialist. 52, 53
• Some specialists treat all cardiovascular syphilis with a neurosyphilis regimen. 52, 54

2.4 Neurosyphilis (including Ocular and Otic Involvement)

• Standard regimen – Aqueous crystalline penicillin G 18–24 million units per day (3–4 million units IV every 4 h or continuous infusion) for 10–14 days. 52, 53
• Ocular syphilis is classified as neurosyphilis and requires the same regimen. 52, 53
• Alternative (if compliance assured) – Procaine penicillin G 2.4 million units IM daily plus probenecid 500 mg PO QID for 10–14 days. Some experts add benzathine penicillin G 2.4 million units IM weekly for up to 3 weeks after completion. 52, 55
• Penicillin‑allergic patients – Penicillin desensitization is the preferred approach; no truly acceptable non‑penicillin alternatives. Ceftriaxone 2 g IV daily for 10–14 days may be considered, but data are limited. 55

3. Special Populations

3.1 Pregnancy

• Penicillin desensitization is required for penicillin‑allergic pregnant patients; penicillin remains the only acceptable therapy. 57
• Penicillin is the sole regimen that prevents maternal‑fetal transmission and treats fetal infection. 57
• Some experts recommend a second 2.4 million‑unit IM dose one week after the initial dose for early syphilis in pregnancy. 57
• All pregnant women should be screened serologically at the first prenatal visit, with repeat testing at 28 weeks and at delivery in high‑prevalence settings. 57

3.2 HIV‑Infected Patients

• Early syphilis in HIV‑positive individuals is treated with the same single 2.4 million‑unit IM dose of benzathine penicillin as HIV‑negative patients. 55
• Enhanced follow‑up with clinical and serologic assessments at 3, 6, 9, 12, and 24 months is essential. 57, 51
• For late latent syphilis, a CSF examination should be performed before treatment; if CSF is normal, treat with three weekly benzathine penicillin G 2.4 million‑unit IM doses. 57, 55

3.3 Pediatrics

• Early syphilis – Benzathine penicillin G 50,000 units/kg IM single dose (maximum 2.4 million units). 51
• Late latent syphilis – Benzathine penicillin G 50,000 units/kg IM weekly for three weeks (maximum 7.2 million units total).
• CSF examination is recommended before treatment to exclude neurosyphilis. 51
• Child‑protection services should be consulted for all children with acquired syphilis. 51

4. Follow‑Up Monitoring

4.1 Early Syphilis

• Clinical and serologic evaluations at 3, 6, 9, 12, and 24 months after therapy. 51
• A ≥4‑fold decline in nontreponemal titers should occur within 6 months of adequate therapy.

4.2 Late Latent Syphilis

• Quantitative nontreponemal serologic testing at 6, 12, and 24 months. 54, 53
• Perform CSF examination if titers increase ≥4‑fold, an initial high titer (≥1:32) fails to decline ≥4‑fold within 12–24 months, or neurologic/ophthalmic signs develop. 54, 53

4.3 Neurosyphilis

• If baseline CSF pleocytosis is present, repeat lumbar puncture every 6 months until cell count normalizes. 55
• Consider retreatment if CSF cell count has not decreased after 6 months or remains abnormal after 2 years. 55

5. Management of Treatment Failure

• Re‑evaluate for HIV infection in any patient with inadequate serologic response.
• Perform a CSF examination to rule out occult neurosyphilis. 51
• If neurosyphilis is excluded, retreat with benzathine penicillin G 2.4 million units IM weekly for 3 weeks. 51

6. Critical Pitfalls

• Pregnant patients: Non‑penicillin alternatives must never be used; desensitization is mandatory. 57
• Azithromycin: Should never be used for syphilis treatment in the United States because of widespread macrolide‑resistant T. pallidum. 51
• Close follow‑up is required for all non‑penicillin regimens because efficacy data are limited compared with penicillin. 52, 53

CDC Guidelines for Treatment of Late Latent Syphilis

Standard Treatment Regimen

• The definitive therapy for late latent syphilis (infection ≥ 1 year or of unknown duration) is benzathine penicillin G 2.4 million units administered intramuscularly once weekly for three consecutive weeks (total 7.2 million units)【58】【59】【60】.
• This three‑dose schedule is required because the infection has persisted for ≥ 1 year or its duration cannot be determined【60】.
• The same three‑dose benzathine penicillin regimen is recommended for both HIV‑infected and HIV‑negative patients with late latent disease【61】.

Pre‑Treatment Clinical Evaluation

• All patients should be clinically assessed for signs of tertiary syphilis (e.g., aortitis, gumma, iritis) before initiating therapy【58】【59】【60】.
• Examination of accessible mucosal surfaces (oral cavity, perineum in women, foreskin in uncircumcised men) is advised to detect internal mucosal lesions【60】.

Indications for Lumbar Puncture

• Perform a cerebrospinal fluid (CSF) examination before treatment if any neurologic manifestations are present (cranial nerve palsies, meningitis, cognitive changes, stroke)【58】【59】【60】.
• Ophthalmic manifestations (uveitis, neuroretinitis, optic neuritis) also mandate CSF evaluation【58】【59】【60】.
• Evidence of active tertiary syphilis (aortitis, gumma, iritis) is an indication for CSF examination【58】【59】【60】.
• Rising or persistently elevated nontreponemal titers suggesting treatment failure require CSF testing【58】【59】【60】.
• HIV infection with late latent syphilis or syphilis of unknown duration is another indication for pre‑treatment CSF examination【58】【59】【61】【62】.
• Some experts recommend CSF examination for all patients whose nontreponemal titers are ≥ 1:32, although the neurosyphilis risk at this threshold remains uncertain【59】【60】.

If CSF findings are consistent with neurosyphilis, treat with the neurosyphilis regimen (aqueous crystalline penicillin G 18–24 million units per day intravenously for 10–14 days) rather than the late latent schedule【58】【59】【60】.

Alternative Regimens for Penicillin‑Allergic, Non‑Pregnant Patients

• Doxycycline 100 mg orally twice daily for 28 days is the only acceptable non‑penicillin alternative【58】【59】【63】.
• If doxycycline cannot be used, tetracycline 500 mg orally four times daily for 28 days is a second‑line option【58】【59】.
• Oral alternatives require close serologic and clinical follow‑up because efficacy data are limited compared with penicillin【59】【63】.

Pregnancy Considerations

• Pregnant patients with a penicillin allergy must undergo desensitization and receive penicillin therapy; no alternative regimens are acceptable【58】【59】【61】.
• Penicillin is the only treatment that both prevents maternal‑fetal transmission and treats established fetal infection【61】.
• Any missed dose in a pregnant woman mandates restarting the full three‑dose benzathine penicillin course【59】【60】.

Management of HIV‑Infected Patients

• Perform a CSF examination before treating HIV‑positive patients with late latent syphilis【62】【61】.
• If CSF results are normal, administer the standard three weekly doses of benzathine penicillin G 2.4 million units IM【62】【61】.
• Enhanced follow‑up is essential, with clinical and serologic assessments at 6, 12, 18, and 24 months【62】【61】.
• Failure of nontreponemal titers to decline fourfold between 12 and 24 months should prompt repeat CSF examination and appropriate retreatment【62】【61】.

Pediatric Dosing

• Children with late latent syphilis receive benzathine penicillin G 50,000 units/kg IM weekly for three weeks (maximum 2.4 million units per dose; total up to 7.2 million units)【58】【59】【60】.
• A CSF examination should be performed before treatment to exclude neurosyphilis【58】【59】【60】.
• Review of birth and maternal medical records is required to differentiate congenital from acquired syphilis【58】【59】【60】.

Missed Dose Policy

• For non‑pregnant patients, an interval of 10–14 days between doses may be acceptable before restarting the injection sequence【59】【60】.

Follow‑Up Monitoring

• Obtain quantitative nontreponemal serologic tests (RPR or VDRL) at 6, 12, and 24 months after treatment【58】【59】【60】.

Criteria for Retreatment

• Retreatment is indicated if any of the following occur:
  
  • A fourfold increase in nontreponemal titers at any time【58】【59】【60】.
  • An initially high titer (≥ 1:32) fails to decline at least fourfold within 12–24 months【58】【59】【60】.
  • Development of signs or symptoms attributable to syphilis【58】【59】【60】.
• Prior to retreatment, a CSF examination must be performed to exclude neurosyphilis【58】【59】【60】.

Concurrent HIV Testing

• All patients diagnosed with syphilis should be tested for HIV infection at the time of syphilis diagnosis【60】.

Critical Pitfalls

• Non‑penicillin alternatives must never be used in pregnant patients; desensitization to penicillin is mandatory regardless of allergy history【58】【59】【61】.
• Azithromycin is contraindicated for syphilis treatment in the United States because of widespread macrolide‑resistant Treponema pallidum and documented treatment failures【63】.
• Persistent low‑titer seropositivity should not be interpreted as treatment failure, as some patients remain “serofast” despite adequate therapy【63】.