Syphilis Treatment Guidelines

Introduction to Syphilis Treatment

• Parenteral penicillin G is the preferred drug for treatment of all stages of syphilis, with the specific preparation, dosage, and duration determined by the stage of infection 1

Treatment Regimens

• For primary and secondary syphilis, benzathine penicillin G, 2.4 million units IM in a single dose, is recommended 2, 1
• For early latent syphilis, benzathine penicillin G, 2.4 million units IM in a single dose, is recommended 1
• Early latent syphilis is defined as syphilis acquired within the preceding year based on documented seroconversion, fourfold increase in titer, history of symptoms, or having a sex partner with documented early syphilis 3

Late-Stage Syphilis Treatment

• For late latent syphilis or latent syphilis of unknown duration, benzathine penicillin G, 7.2 million units total, administered as 3 doses of 2.4 million units IM each at 1-week intervals, is recommended 1
• For tertiary syphilis, benzathine penicillin G, 7.2 million units total, administered as 3 doses of 2.4 million units IM each at 1-week intervals, is recommended 1

Neurosyphilis Treatment

• Aqueous crystalline penicillin G is recommended for neurosyphilis treatment 2, 4
• CSF examination is recommended for diagnosing neurosyphilis in patients with neurological signs/symptoms, tertiary syphilis, or those whose serological titers fail to decline appropriately 1

Alternative Treatments

• For penicillin-allergic non-pregnant adults with primary and secondary syphilis, doxycycline 100 mg orally twice daily for 14 days is recommended 1
• For penicillin-allergic non-pregnant adults with late latent syphilis, doxycycline 100 mg orally twice daily for 28 days is recommended 1
• For pregnant women and neurosyphilis patients, penicillin remains the only proven effective therapy, and patients should undergo desensitization if they report penicillin allergy 2, 4, 1

Special Populations

• HIV-infected patients have the same treatment regimens as non-HIV-infected patients 1
• HIV-infected patients may have atypical serologic responses but generally respond well to standard treatment 4, 5
• For pregnant women, parenteral penicillin G is the only therapy with documented efficacy for preventing maternal transmission 2, 1

Follow-Up and Monitoring

• Quantitative nontreponemal serologic tests should be repeated at regular intervals (3, 6, 12, and 24 months) 1
• A fourfold decline in titer is expected within 6 months for primary/secondary syphilis and within 12-24 months for late syphilis 1
• Treatment failure is defined as failure of nontreponemal test titers to decline fourfold within 6 months after therapy for primary or secondary syphilis 1

Management of Sex Partners

• Persons exposed within 90 days preceding the diagnosis of primary, secondary, or early latent syphilis should be treated presumptively even if seronegative 2, 6
• Persons exposed >90 days before diagnosis should be treated presumptively if serologic test results are not immediately available and follow-up is uncertain 2, 5

Important Clinical Considerations

• The Jarisch-Herxheimer reaction is an acute febrile reaction that may occur within 24 hours after any syphilis therapy, especially in early syphilis 2, 6
• Patients should be informed about this possible adverse reaction, which may include headache, myalgia, and other symptoms 2

Pitfalls to Avoid

• Do not use oral penicillin preparations for syphilis treatment as they are ineffective 4
• Do not rely solely on treponemal test antibody titers to assess treatment response, as they correlate poorly with disease activity 7, 8
• Do not use different testing methods (e.g., switching between VDRL and RPR) when monitoring serologic response, as results cannot be directly compared 7, 8

Syphilis Treatment Guidelines

Follow-Up and Monitoring

• If treatment failure is suspected, patients should be re-evaluated for HIV infection and undergo CSF examination 9

Syphilis Treatment Guidelines

Treatment Considerations

• If a dose is missed during weekly therapy, an interval of 10-14 days between doses might be acceptable before restarting the sequence, as recommended by the Centers for Disease Control and Prevention 10

Syphilis Management in Special Populations

Treatment Recommendations

• The Centers for Disease Control and Prevention recommends that all pregnant women with penicillin allergy MUST undergo desensitization followed by penicillin treatment 11
• For late latent syphilis with HIV and normal CSF, the Centers for Disease Control and Prevention recommends benzathine penicillin G 7.2 million units (three weekly doses of 2.4 million units each) 11
• The Centers for Disease Control and Prevention recommends screening all pregnant women for syphilis at first prenatal visit, during third trimester, and at delivery 11
• The Centers for Disease Control and Prevention warns that Jarisch-Herxheimer reaction during second half of pregnancy may precipitate premature labor or fetal distress 11
• The Centers for Disease Control and Prevention advises that women should seek immediate medical attention if they notice changes in fetal movements or contractions after treatment 11
• The Centers for Disease Control and Prevention states that only penicillin prevents congenital syphilis, and therefore, never substitute with inadequate alternatives in pregnancy 11

Treatment of Syphilis with Antibiotics

Special Considerations

• Azithromycin should NOT be used in the United States due to widespread macrolide resistance and documented treatment failures, despite some evidence of efficacy in low-resistance areas, according to the Clinical Infectious Diseases 12
• Ceftriaxone 1 gram IV/IM daily for 10 days is a reasonable alternative based on randomized trial data showing comparable efficacy to benzathine penicillin, as reported in the Clinical Infectious Diseases 12
• Limited data suggest no benefit to multiple doses of benzathine penicillin for early syphilis in HIV-infected patients compared to a single dose, as found in the Clinical Infectious Diseases 12
• Closer follow-up is mandatory to detect potential treatment failure or disease progression in HIV-infected patients, as recommended by the MMWR Recommendations and Reports 13

Syphilis Treatment Guidelines

Diagnosis and Treatment

• The Centers for Disease Control and Prevention recommends that early latent syphilis is defined as syphilis acquired within the preceding year, documented by seroconversion, fourfold increase in titer, history of symptoms of primary or secondary syphilis within the past year, or having a sex partner with documented early syphilis 14, 15
• For pediatric patients with early latent syphilis, the American Academy of Pediatrics recommends benzathine penicillin G 50,000 units/kg IM, up to the adult dose of 2.4 million units in a single dose 14, 15
• For pediatric patients with late latent syphilis, the American Academy of Pediatrics recommends benzathine penicillin G 50,000 units/kg IM, up to the adult dose of 2.4 million units, for three total doses at 1-week intervals (total 150,000 units/kg up to adult total dose of 7.2 million units) 14, 15

Special Populations

• Pregnant women who are penicillin-allergic must undergo desensitization followed by penicillin treatment, as recommended by the Centers for Disease Control and Prevention 14, 15

Syphilis Treatment Guidelines

Diagnosis and Treatment

• The Centers for Disease Control and Prevention recommends administering benzathine penicillin G 2.4 million units intramuscularly as a single dose for primary and secondary syphilis in adults 16, 17
• All patients with syphilis should be tested for HIV infection, as recommended by the Centers for Disease Control and Prevention 16, 17
• For children with acquired syphilis, the recommended dose is benzathine penicillin G 50,000 units/kg IM (up to adult dose of 2.4 million units) as a single dose, according to the Centers for Disease Control and Prevention 16, 17
• Children require CSF examination to exclude neurosyphilis before treatment, as recommended by the Centers for Disease Control and Prevention 16, 17

Latent Syphilis

• The Centers for Disease Control and Prevention recommends treating early latent syphilis with benzathine penicillin G 2.4 million units IM as a single dose 18
• For late latent syphilis or latent syphilis of unknown duration, the recommended treatment is benzathine penicillin G 7.2 million units total as three doses of 2.4 million units IM at weekly intervals, according to the Centers for Disease Control and Prevention 18
• Pre-treatment CSF examination is indicated for patients with neurologic or ophthalmic signs or symptoms, evidence of active tertiary syphilis, treatment failure, HIV infection with late latent syphilis or syphilis of unknown duration, or serum nontreponemal titer ≥1:32, as recommended by the Centers for Disease Control and Prevention 17, 18

Neurosyphilis

• The recommended treatment for neurosyphilis is aqueous crystalline penicillin G 18-24 million units per day IV (administered as 3-4 million units every 4 hours or continuous infusion) for 10-14 days, although the citation is not provided

Penicillin Allergy Alternatives

• For penicillin-allergic non-pregnant adults with primary, secondary, or early latent syphilis, the recommended alternative treatment is doxycycline 100 mg orally twice daily for 14 days, according to the Centers for Disease Control and Prevention 18
• For penicillin-allergic non-pregnant adults with late latent syphilis, the recommended alternative treatment is doxycycline 100 mg orally twice daily for 28 days, as recommended by the Centers for Disease Control and Prevention 18
• Tetracycline 500 mg orally four times daily is an alternative treatment for 14 days for early latent syphilis and 28 days for late latent syphilis, according to the Centers for Disease Control and Prevention 18

Follow-Up Protocol

• The Centers for Disease Control and Prevention recommends performing quantitative nontreponemal serologic tests (RPR or VDRL) at 6 and 12 months after treatment for primary/secondary syphilis 16, 17
• For latent syphilis, repeat quantitative nontreponemal tests at 6, 12, and 24 months, as recommended by the Centers for Disease Control and Prevention 18
• Re-treat and evaluate for HIV if any of the following occur: persistent or recurring signs/symptoms, sustained fourfold increase in nontreponemal titers, or failure of initially high titer to decline at least fourfold within 6-12 months for early syphilis or 12-24 months for late syphilis, according to the Centers for Disease Control and Prevention 16, 17, 18

Management of Sex Partners

• The Centers for Disease Control and Prevention recommends treating sex partners presumptively if exposed within 90 days preceding diagnosis of primary, secondary, or early latent syphilis, even if seronegative, although the citation is not provided
• Time periods for at-risk partners: 3 months plus duration of symptoms for primary syphilis, 6 months plus duration of symptoms for secondary syphilis, and 1 year for early latent syphilis, as recommended by the Centers for Disease Control and Prevention 16, 17

Syphilis Treatment Guidelines

Recommended Treatment Regimens

• The Centers for Disease Control and Prevention (CDC) recommends procaine penicillin G (with probenecid) as an alternative for neurosyphilis treatment, as stated in the MMWR Recommendations and Reports 19
• Aqueous crystalline penicillin G 18-24 million units IV daily for 10-14 days is a recommended treatment for neurosyphilis, according to the MMWR Recommendations and Reports 19
• Ceftriaxone 1 gram IM/IV daily for 10 days may be considered for syphilis treatment, based on randomized trial data showing comparable efficacy to benzathine penicillin, as reported in Clinical Infectious Diseases 20
• The use of azithromycin is not recommended in the United States due to widespread macrolide resistance and documented treatment failures, as stated in Clinical Infectious Diseases 20

Treatment of Neurosyphilis

• Procaine penicillin without probenecid does not achieve adequate CSF levels and is inadequate for neurosyphilis treatment, according to the MMWR Recommendations and Reports 19

Syphilis Treatment Guidelines

Pregnancy Considerations

• The Centers for Disease Control and Prevention recommends that all pregnant women with penicillin allergy MUST undergo desensitization followed by penicillin treatment—no exceptions, as penicillin is the only therapy with documented efficacy for preventing maternal transmission to the fetus and treating fetal infection 21
• Penicillin is the only therapy with documented efficacy for preventing maternal transmission to the fetus and treating fetal infection, and some experts recommend a second dose of benzathine penicillin 2.4 million units IM administered 1 week after the initial dose for women with primary, secondary, or early latent syphilis 21
• Women treated during the second half of pregnancy are at risk for premature labor and/or fetal distress from Jarisch-Herxheimer reaction; they should seek immediate medical attention if they notice contractions or changes in fetal movements 21
• Tetracycline, doxycycline, erythromycin, azithromycin, and ceftriaxone are inadequate—erythromycin does not reliably cure fetal infection 21

HIV-Infected Patients

• The Centers for Disease Control and Prevention recommends that penicillin regimens should be used for all stages of syphilis in HIV-infected patients 21
• Patients with penicillin allergy should undergo skin testing and desensitization, then be treated with penicillin 21

Treatment of Syphilis

Diagnosis and Treatment

• Unless reinfection is likely, lumbar puncture should be performed to evaluate for neurosyphilis in cases of treatment failure, according to the MMWR Recommendations and Reports 22
• Re-treatment typically involves three weekly injections of benzathine penicillin G 2.4 million units IM, unless CSF examination indicates neurosyphilis, as recommended by the MMWR Recommendations and Reports 22

Ceftriaxone for Syphilis Treatment

Introduction to Ceftriaxone Use

• The Centers for Disease Control and Prevention recommends ceftriaxone 1 gram IM daily for 10-14 days as an alternative treatment for syphilis in penicillin-allergic patients, though it remains a second-line option with limited data compared to penicillin, and should be reserved for situations where penicillin desensitization is not feasible 23

Dosing and Duration

• The recommended ceftriaxone regimen is 1 gram daily (IM or IV) for 10-14 days for early syphilis 23
• For neurosyphilis, ceftriaxone 2 grams daily IV for 10-14 days has limited supporting data but may be considered 24, 23

Critical Limitations and Caveats

• Patients with severe penicillin allergy (such as Stevens-Johnson syndrome) may also be allergic to ceftriaxone, as both are beta-lactam antibiotics 25
• The optimal dose and duration of ceftriaxone have not been definitively established 25
• Evidence for ceftriaxone in late latent syphilis and tertiary syphilis is extremely limited 25
• Efficacy data in HIV-infected patients, while promising, remain limited compared to penicillin 24, 26

Neurosyphilis Treatment

• If ceftriaxone must be used for neurosyphilis, the dose is 2 grams daily IV (not IM) for 10-14 days, with very limited supporting data 24, 23

Common Pitfalls to Avoid

• Do not use azithromycin in the United States due to widespread macrolide resistance and documented treatment failures 23
• Remember that 15-25% of successfully treated patients remain "serofast" with persistent low titers (<1:8) that do not indicate treatment failure 23

CDC Guidelines for Syphilis Treatment and Management

Primary and Secondary Syphilis – First‑Line Therapy

Early Latent Syphilis (≤ 1 year) – First‑Line Therapy

Late Latent and Tertiary Syphilis (> 1 year or unknown duration) – First‑Line Therapy

Neurosyphilis – Diagnostic Requirement

Alternative Regimens for Penicillin‑Allergic Patients

Early Syphilis (non‑pregnant adults)

Late Latent Syphilis (non‑pregnant adults)

Pregnant Patients with Penicillin Allergy

Follow‑Up and Monitoring

Late Latent Syphilis

Treatment Failure Indicators

Management of Sex Partners

HIV Testing Recommendations

CDC 2004 Recommendations for Neurosyphilis Treatment

First‑Line Penicillin Therapy

• Intravenous aqueous crystalline penicillin G (18–24 million U/day, given as 3–4 million U every 4 h or by continuous infusion) for 10–14 days achieves cerebrospinal‑fluid (CSF) penicillin concentrations sufficient to eradicate Treponema pallidum from the central nervous system. [CDC MMWR 2004] 30
• Some clinicians add three weekly intramuscular doses of benzathine penicillin G 2.4 million U after the IV course to provide additional coverage, although a consensus on this practice has not been reached. [CDC MMWR 2004] 30

Alternative Penicillin‑Based Regimens (Outpatient Option)

• Procaine penicillin 2.4 million U IM once daily plus probenecid 500 mg orally four times daily for 10–14 days is an acceptable alternative when adherence can be assured. [CDC MMWR 2004] 30
• Procaine penicillin without probenecid is inadequate because it fails to achieve therapeutic CSF penicillin levels. [CDC MMWR 2004] 30
• Patients with known sulfonamide allergy should not receive the procaine‑penicillin + probenecid regimen, as they are highly likely to be allergic to probenecid. [CDC MMWR 2004] 30

Evidence Strength

• The above recommendations are based on expert consensus and epidemiologic data compiled by the CDC in its 2004 MMWR report; the report classifies the evidence as moderate‑quality expert opinion rather than randomized controlled trial data. 30

Guideline Summary for Evaluation and Management of Penile Lesions After Recent Syphilis Treatment

Diagnosis and Differential Considerations

Serologic Monitoring and Treatment‑Failure Assessment

Management Recommendations

Common Pitfalls to Avoid

Management of Penicillin Allergy in Primary Syphilis

Alternative Regimens

• Erythromycin 500 mg orally four times daily for 14 days is less effective than other regimens and should be used only when strict compliance and reliable follow‑up can be guaranteed. (CDC MMWR recommendation; expert opinion) 33

Desensitization

• If patient compliance with any non‑penicillin regimen or reliable follow‑up cannot be assured, penicillin desensitization is strongly recommended, followed by the standard benzathine penicillin G 2.4 million U IM dose. (CDC MMWR recommendation; expert opinion) 33

Allergy Testing

• Skin testing for penicillin allergy may be performed to clarify true allergy status before proceeding with desensitization. (CDC MMWR recommendation; expert opinion) 33

CDC Guidelines for Syphilis Treatment and Management

Early Latent Syphilis (≤ 1 year) – Definition

• Early latent syphilis is defined by any of the following: documented seroconversion within the past year, unequivocal primary/secondary symptoms occurring within the past year, or a sexual partner with confirmed early syphilis. [CDC, 2002] 34

Late Latent Syphilis and Syphilis of Unknown Duration – CSF Evaluation

• A lumbar puncture is recommended before therapy when any of these are present: neurologic or ophthalmic signs, evidence of active tertiary disease, prior treatment failure, HIV infection with late latent disease, or a nontreponemal titer ≥ 1:32. [CDC, 2002] 34

Neurosyphilis – Follow‑Up and Retreatment Criteria

• If cerebrospinal fluid (CSF) pleocytosis was documented at baseline, repeat CSF analysis every 6 months until the white‑cell count normalizes. [CDC, 2004] 35
• Consider retreatment when the CSF white‑blood‑cell count has not decreased after 6 months or when CSF abnormalities persist beyond 2 years. [CDC, 2004] 35

Syphilis in Pregnancy – Treatment Imperatives

• All pregnant patients must receive the penicillin regimen appropriate for the disease stage, administered > 4 weeks before delivery to optimize fetal outcomes. [CDC, 2004] 35
• Women with a documented penicillin allergy must undergo desensitization and receive penicillin; no alternative regimen has proven efficacy for preventing congenital syphilis. [CDC, 2004] 35
• For primary, secondary, or early latent infection, an additional dose of benzathine penicillin 2.4 million units IM one week after the initial dose may be given. [CDC, 2004] 35
• Erythromycin, tetracyclines, azithromycin, and ceftriaxone are not reliable alternatives for treating maternal or fetal infection. [CDC, 2004] 35
• Jarisch‑Herxheimer reactions occurring in the second half of pregnancy can precipitate preterm labor or fetal distress; obstetric monitoring for 24 hours after therapy is advised for women > 20 weeks gestation. [CDC, 2004] 35
• Routine syphilis screening is recommended at the first prenatal visit, at 28 weeks gestation, and at delivery; maternal serology must be documented before infant discharge. [CDC, 2004] 35

Syphilis in HIV‑Infected Patients – Management Nuances

• HIV‑positive individuals receive the same penicillin regimens as HIV‑negative patients for all disease stages. [CDC, 2004] 35
• More intensive post‑treatment monitoring is required: clinical and serologic evaluation at 3, 6, 9, 12, and 24 months. [CDC, 2004] 35
• For late latent syphilis, a CSF examination should be considered before therapy to exclude neurosyphilis. [CDC, 1993] 36
• When CSF is normal after treatment failure, most experts retreat with benzathine penicillin 7.2 million units (three weekly doses). [CDC, 1993] 36
• Penicillin‑allergic HIV‑infected patients should undergo skin testing and desensitization before receiving penicillin. [CDC, 2004; 1993] [35][36]

Treatment Failure – Evaluation and Retreatment Strategy

• If CSF findings are normal after a failed regimen, retreat with benzathine penicillin 7.2 million units administered as three weekly IM doses. [CDC, 1993] 36
• When CSF remains abnormal after failure of the standard regimen, manage according to the neurosyphilis protocol (IV aqueous crystalline penicillin). [CDC, 2004] 35

CDC Guidelines for Syphilis Management (Cited Evidence)

Primary Syphilis Clinical Features

• The primary syphilitic chancre is characteristically painless, so specific analgesic therapy is not required. This clinical feature helps differentiate syphilis from other genital ulcer diseases. 37

Treatment in Pregnancy

• All pregnant individuals diagnosed with syphilis must receive the penicillin regimen appropriate for the disease stage, without any exceptions. (Population: pregnant patients; Intervention: stage‑specific penicillin; Outcome: appropriate treatment). 37
• Parenteral penicillin G is the only therapy with documented efficacy for preventing congenital syphilis and for treating fetal infection. (Population: pregnant patients with syphilis; Intervention: parenteral penicillin G; Outcome: prevention of congenital disease). 37
• Pregnant patients with a documented penicillin allergy must undergo skin‑test‑guided desensitization followed by penicillin therapy. (Population: pregnant patients with penicillin allergy; Intervention: desensitization + penicillin; Outcome: safe and effective treatment). 37

Jarisch‑Herxheimer Reaction

• The Jarisch‑Herxheimer reaction is an acute febrile reaction—often accompanied by headache, myalgia, and other systemic symptoms—that can occur within the first 24 hours after any syphilis therapy. (Population: patients receiving syphilis treatment; Intervention: any antimicrobial therapy; Outcome: acute reaction). 37
• This reaction occurs most commonly in patients with early‑stage syphilis (primary, secondary, or early latent). (Population: early syphilis patients; Outcome: higher incidence of reaction). 37
• No proven preventive measures exist; however, antipyretics may be used for symptom relief. (Intervention: antipyretics; Outcome: symptomatic management). 37
• Patients should be counseled about the possibility of a Jarisch‑Herxheimer reaction before initiating therapy. (Outcome: informed consent and preparedness). 37

Management of Sexual Partners

• Sexual partners exposed within 90 days before the index case’s diagnosis of primary, secondary, or early latent syphilis should receive presumptive treatment with a single dose of benzathine penicillin G 2.4 million units, even if serologic testing is negative. (Population: recent contacts; Intervention: presumptive benzathine penicillin; Outcome: prevention of transmission). 37
• Partners exposed more than 90 days prior should also receive presumptive treatment when serologic results are unavailable and reliable follow‑up cannot be ensured. (Population: earlier contacts; Intervention: presumptive treatment; Outcome: infection control). 37

CDC Guidelines for Doxycycline Use in Penicillin‑Allergic Syphilis Patients

Dosing Recommendations

• Early syphilis (primary, secondary, or early latent ≤ 1 year) – prescribe doxycycline 100 mg orally twice daily for 14 days as the first‑line oral alternative when penicillin cannot be used. [38][39]
• Late latent syphilis or syphilis of unknown duration (> 1 year) – prescribe doxycycline 100 mg orally twice daily for 28 days as the sole acceptable oral alternative. [38][39]40
• Tertiary syphilis (gummatous or cardiovascular) – treat according to the late‑latent regimen (doxycycline 100 mg orally twice daily for 28 days). 40

Alternative Oral Regimens

• Early syphilis – tetracycline 500 mg orally four times daily for 14 days is an acceptable alternative, but doxycycline is preferred because of better adherence and fewer gastrointestinal side effects. [41][42]
• Late latent syphilis – tetracycline 500 mg orally four times daily for 28 days is also acceptable. [38][42]
• When both penicillin and doxycycline are contraindicated – tetracycline 500 mg orally four times daily (14 days for early disease, 28 days for late latent) is the next option. [41][42]
• Early syphilis (penicillin‑allergic) – ceftriaxone 1 g intramuscularly or intravenously daily for 8–10 days may be considered; data are limited and cross‑reactivity with penicillin allergy is possible. 39

Contraindications & Mandatory Diagnostic Steps

• Pregnancy – doxycycline is absolutely contraindicated; all pregnant patients with a penicillin allergy must undergo penicillin desensitization and receive penicillin therapy. [38][39][42][40]
• Neurosyphilis risk – before initiating any non‑penicillin regimen, a cerebrospinal fluid (CSF) examination must be performed to exclude neurosyphilis. 39
• Tertiary syphilis – CSF examination is mandatory before treatment to rule out neurosyphilis. 40

Monitoring and Treatment Success

• Patients treated with doxycycline require quantitative non‑treponemal serologic testing (RPR or VDRL) at 6, 12, and 24 months due to limited long‑term efficacy data compared with penicillin. [38][39]
• For late latent syphilis, a four‑fold decline in non‑treponemal titers is expected within 12–24 months. [38][39]

Special Populations

• HIV‑infected patients – receive the same doxycycline regimens (14 days for early disease, 28 days for late latent). [38][39]
• Efficacy data for doxycycline in HIV‑positive individuals are limited; therefore, closer surveillance is recommended. [38][40]

Key Clinical Pitfalls (What to Avoid)

• Do not use doxycycline in pregnancy under any circumstances; desensitization to penicillin is mandatory. [38][39]
• Do not shorten the 28‑day course for late latent syphilis; the full duration is essential for adequate treatment. [38][39]40
• Do not skip the CSF examination before treating late latent syphilis with doxycycline, as undiagnosed neurosyphilis will not respond to oral therapy. 39

CDC Neurosyphilis Management Guidelines

First‑Line Penicillin Therapy

• Intravenous aqueous crystalline penicillin G at a total daily dose of 18–24 million units, given either as 3–4 million units IV every 4 hours or as a continuous infusion, for 10–14 days is the CDC’s preferred regimen for neurosyphilis. This dosing achieves cerebrospinal‑fluid (CSF) concentrations that eradicate Treponema pallidum and is supported by strong CDC recommendations. [43][44]45
• Optional supplemental benzathine penicillin G (2.4 million units IM weekly for up to 3 weeks) may be added after the IV course to match the total treatment duration used for late‑latent syphilis, although consensus on this practice is lacking. [44][45]

Alternative Outpatient Regimen (Procaine Penicillin + Probenecid)

• For patients who can reliably attend daily visits, procaine penicillin 2.4 million units IM once daily plus probenecid 500 mg orally four times daily for 10–14 days is an acceptable alternative, provided probenecid is used to ensure adequate CSF penicillin levels. [44][45]
• Probenecid is mandatory; omitting it results in subtherapeutic CSF concentrations and treatment failure. 44
• Sulfonamide allergy (e.g., to sulfonamide drugs) contraindicates this regimen because of likely cross‑reactivity with probenecid. 44

Management of Penicillin Allergy

• Penicillin desensitization followed by any standard CDC‑recommended penicillin regimen is the preferred approach for patients with a penicillin allergy. 44
• Ceftriaxone 2 g IV daily for 10–14 days may be considered when desensitization is not feasible, but evidence is extremely limited (very low‑quality data from a single small trial). 44

Follow‑Up and CSF Monitoring

• When initial CSF pleocytosis is present, repeat lumbar puncture every 6 months until the white‑cell count normalizes; the CSF WBC count is the most sensitive marker of treatment response. [44][45]
• CSF VDRL and protein changes occur more slowly and persistent abnormalities are less predictive of treatment failure. 45
• Retreatment criteria:
  
  • If the CSF cell count has not decreased after 6 months, retreatment is recommended. [44][45]
  • If CSF remains abnormal after 2 years, retreatment is also advised. 44
• The retreatment regimen mirrors the first‑line therapy (aqueous crystalline penicillin G 18–24 million units IV daily for 10–14 days).

HIV‑Coinfected Patients

• Treatment: HIV‑positive individuals receive the same penicillin regimens (IV aqueous crystalline penicillin G or procaine + probenecid) as HIV‑negative patients. 44
• Enhanced monitoring: Clinical and serologic evaluations are recommended at 3, 6, 9, 12, and 24 months post‑treatment due to higher rates of atypical serologic responses and treatment failure. 44
• CSF examination should be considered before therapy for late‑latent syphilis in HIV‑infected patients, and many experts advocate CSF testing for all HIV‑positive syphilis cases regardless of stage. 44

Indications for Pre‑Treatment CSF Examination

• Neurologic manifestations (e.g., cognitive dysfunction, motor or sensory deficits, cranial nerve palsies, meningismus). 45
• Ophthalmic involvement (uveitis, neuroretinitis, optic neuritis). [44][45]
• Auditory symptoms. 45
• Evidence of active tertiary syphilis (aortitis, gummas, iritis). 43
• Documented treatment failure (persistent symptoms or rising serologic titers). 43
• HIV infection with late‑latent syphilis or syphilis of unknown duration. [43][44]

Medication Selection Pitfalls (Safety Alerts)

• Never use procaine penicillin without probenecid for neurosyphilis; CSF levels will be inadequate. 44
• Never use oral penicillin preparations for any stage of syphilis.
• Never use azithromycin because of widespread macrolide resistance and documented treatment failures.
• Do not substitute non‑penicillin agents in pregnancy; penicillin remains the only proven therapy to prevent congenital syphilis.

All recommendations reflect CDC guideline statements and are presented with the strength of evidence as indicated in the source documents (generally strong recommendations for penicillin regimens; very low‑quality evidence for ceftriaxone).

Guideline Recommendations for Syphilis Treatment and Alternatives

First‑Line Therapy with Benzathine Penicillin G

Ceftriaxone as a Second‑Line Alternative (Non‑Pregnant, Penicillin‑Allergic Patients)

Pregnancy‑Specific Contraindications

Decision‑Making Algorithm for Penicillin Allergy

Regimen Requirements and Evidence Strength

CDC Recommendations for Ceftriaxone Use in Penicillin‑Allergic Syphilis Patients

Neurosyphilis (when penicillin desensitization is not feasible)

• Ceftriaxone 2 g IV once daily for 10–14 days is suggested as an alternative regimen; the recommendation is based on very limited data from small case series, providing low‑level evidence. 49
• Penicillin desensitization remains the preferred approach for neurosyphilis, reflecting higher‑quality evidence and standard of care. 49

Dosing Principles for Ceftriaxone in Syphilis

• A single dose of ceftriaxone is ineffective for any stage of syphilis; a complete 10–14‑day course is required. This conclusion derives from CDC reports (1993) and represents low‑level evidence. 50

Late Latent Syphilis or Syphilis of Unknown Duration

• Evidence supporting ceftriaxone for late latent disease is insufficient; optimal dose and duration have not been established, indicating very low‑level evidence. 50

Partner Management for Early Syphilis

Immediate Presumptive Treatment of Exposed Partners

• CDC recommends that any sexual partner exposed within 90 days of the index patient’s diagnosis of primary, secondary, or early latent syphilis receive a single intramuscular dose of benzathine penicillin G 2.4 million units immediately, irrespective of the partner’s serologic test result. 51
• If exposure occurred more than 90 days before diagnosis, CDC advises presumptive treatment when rapid serologic testing is unavailable and reliable follow‑up cannot be guaranteed. 51
• When serologic testing can be performed promptly and follow‑up is assured, CDC recommends testing first and treating based on the test outcome rather than giving presumptive therapy. 51

Alternative Regimens for Penicillin‑Allergic Non‑Pregnant Partners

• First‑line alternative (CDC): doxycycline 100 mg orally twice daily for 14 days. 52
• Second‑line alternative (CDC): tetracycline 500 mg orally four times daily for 14 days; this option is less preferred because of gastrointestinal side effects and lower adherence rates. 52
• Third‑line alternative (CDC, when adherence can be ensured): ceftriaxone 1 g administered intramuscularly or intravenously once daily for 8–10 days. Cross‑reactivity with penicillin allergy is possible, and the optimal dose and duration have not been definitively established. 52
• If reliable adherence to oral regimens cannot be assured, CDC strongly recommends penicillin desensitization followed by a single dose of benzathine penicillin G 2.4 million units. 52

CDC Recommendations for Syphilis Treatment

Early Syphilis (Primary, Secondary, or Early Latent)

• The Centers for Disease Control and Prevention (CDC) recommends a single intramuscular injection of benzathine penicillin G 2.4 million units for adults with early syphilis (primary, secondary, or early latent ≤ 1 year). This regimen achieves 90–100 % cure rates. 53
• For non‑pregnant adults with a penicillin allergy, the CDC recommends doxycycline 100 mg orally twice daily for 14 days as the first‑line oral alternative for early syphilis. 54
• Tetracycline 500 mg orally four times daily for 14 days is an acceptable alternative to doxycycline, but doxycycline is preferred because of better adherence and fewer gastrointestinal side effects. 54

Late Syphilis (Late Latent, Latent of Unknown Duration, or Tertiary)

• The CDC recommends three weekly intramuscular injections of benzathine penicillin G 2.4 million units (total 7.2 million units) for patients with late latent syphilis, latent syphilis of unknown duration, or tertiary syphilis (gummatous or cardiovascular). [53][55]
• For non‑pregnant adults with a penicillin allergy, doxycycline 100 mg orally twice daily for 28 days is the only acceptable oral regimen for late latent syphilis. [54][55]
• Tetracycline 500 mg orally four times daily for 28 days is also acceptable as an alternative to doxycycline in this setting. [54][55]

Neurosyphilis

• The CDC recommends aqueous crystalline penicillin G 18–24 million units per day administered intravenously (3–4 million units every 4 hours or as a continuous infusion) for 10–14 days for any patient with clinical or laboratory evidence of neurosyphilis. [54][55]
• A lumbar puncture (CSF examination) is mandatory before initiating therapy for patients with neurologic or ophthalmic signs, active tertiary disease, treatment failure, HIV infection with late latent syphilis, or a nontreponemal titer ≥ 1:32. 53
• An outpatient alternative (used only when adherence can be assured) consists of procaine penicillin 2.4 million units intramuscularly once daily plus probenecid 500 mg orally four times daily for 10–14 days; probenecid is required to achieve adequate CSF concentrations. 54
• Some clinicians add benzathine penicillin G 2.4 million units intramuscularly weekly for up to three weeks after completing the IV course to match the total duration used for late latent syphilis, although consensus on this practice is lacking. 55

Special Populations

Persons Living with HIV

• The CDC states that HIV‑infected individuals should receive the same penicillin regimens as HIV‑negative patients for all stages of syphilis. 56
• Post‑treatment monitoring in HIV‑infected patients should be more intensive: quantitative nontreponemal tests at 3, 6, 9, 12, and 24 months (versus 6, 12, 24 months in HIV‑negative patients). 56
• For HIV‑infected patients with late latent syphilis, a CSF examination should be considered before therapy to rule out neurosyphilis. 56
• Although serologic responses may be atypical (higher or lower titers, delayed seroreactivity), HIV‑infected patients generally respond well to standard penicillin treatment. 56
• Penicillin‑allergic HIV‑infected patients should undergo skin testing and, if indicated, desensitization before receiving penicillin. 56

Pregnant Patients

• The CDC requires that all pregnant patients with syphilis receive the appropriate penicillin regimen for their disease stage, administered at least four weeks before delivery to optimize fetal outcomes. (Guideline statement without a specific citation; omitted per instructions.)
• For pregnant patients with a documented penicillin allergy, the CDC mandates penicillin desensitization followed by the standard penicillin regimen; no alternative antibiotics are acceptable because penicillin is the only therapy proven to prevent maternal‑fetal transmission and treat fetal infection. [54][55]

Summary of Evidence Strength