What is the recommended updated therapy for syphilis across its stages?

Updated Therapy for Syphilis

Benzathine penicillin G remains the definitive treatment for all stages of syphilis, with dosing determined by disease stage: a single 2.4 million unit IM injection for early syphilis (primary, secondary, and early latent), and three weekly doses of 2.4 million units IM for late latent and tertiary syphilis. 1

Treatment by Stage

Primary and Secondary Syphilis

• Standard regimen: Benzathine penicillin G 2.4 million units IM as a single dose 1
• Treatment success rates: 90-100% 2
• For HIV-infected patients: Same single-dose regimen is recommended, though some experts suggest additional doses 3, 4
  • Recent evidence shows no significant benefit to multiple doses in HIV-infected patients based on serologic outcomes 4
  • However, closer follow-up is warranted (at 1,2,3,6,9, and 12 months) 3

Early Latent Syphilis (< 1 year duration)

• Standard regimen: Benzathine penicillin G 2.4 million units IM as a single dose 1
• HIV-infected patients should be managed identically to those with primary/secondary syphilis 5

Late Latent and Tertiary Syphilis

• Standard regimen: Benzathine penicillin G 7.2 million units total, administered as three doses of 2.4 million units IM at weekly intervals 1, 3
• Patients with symptomatic late syphilis require CSF examination before initiating therapy 1, 3
• Cardiovascular syphilis may warrant neurosyphilis treatment regimens in consultation with specialists 1

Neurosyphilis

• Standard regimen: 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 1
• Alternative regimen (if compliance assured): Procaine penicillin 2.4 million units IM once daily PLUS probenecid 500 mg orally four times daily, both for 10-14 days 1
• Some specialists add benzathine penicillin 2.4 million units IM weekly for up to 3 weeks after completing neurosyphilis treatment to provide comparable total duration 1
• Critical: Syphilitic uveitis or other ocular manifestations must be treated as neurosyphilis with CSF examination 1

Alternative Regimens for Penicillin Allergy

Early Syphilis (Primary, Secondary, Early Latent)

• Doxycycline 100 mg orally twice daily for 14 days 1, 4, 6
  • Recent systematic review and network meta-analysis supports doxycycline as the best-supported alternative (pooled OR 6.88 favoring doxycycline) 6
• Tetracycline 500 mg orally four times daily for 14 days 1, 3
• Ceftriaxone 1 g IV/IM daily for 10 days is a reasonable alternative based on randomized trial data 4
• Azithromycin is NOT recommended due to widespread macrolide resistance in the United States, despite some efficacy data 4, 7, 8

Late Latent Syphilis

• Doxycycline 100 mg orally twice daily for 28 days 1
• Tetracycline 500 mg orally four times daily for 28 days 1
• CSF examination must exclude neurosyphilis before using non-penicillin therapy 1, 3
• Close serologic and clinical follow-up is essential 1

Neurosyphilis

• No acceptable alternatives exist 3
• Penicillin-allergic patients must undergo desensitization and receive penicillin 3

Special Populations

Pregnancy

• All pregnant patients must receive penicillin regardless of allergy status 5, 1, 3
• Penicillin-allergic pregnant women require desensitization followed by stage-appropriate penicillin regimen 5, 1, 3
• Some experts recommend a second dose of benzathine penicillin 2.4 million units IM one week after initial dose for primary, secondary, or early latent syphilis in pregnancy 5, 3
• Screening requirements: Early pregnancy, 28 weeks gestation, and at delivery in high-prevalence populations 5, 3
• Women treated in the second half of pregnancy risk premature labor from Jarisch-Herxheimer reaction 5, 3

HIV-Infected Patients

• Primary/Secondary/Early Latent: Same single-dose benzathine penicillin G 2.4 million units IM 3
• Late Latent: CSF examination required before treatment; if normal, treat with benzathine penicillin G 7.2 million units (three weekly doses) 5, 3
• Penicillin must be used for all stages—desensitization if allergic 5, 3
• More intensive follow-up required due to potential treatment failure 5, 3

Follow-Up and Treatment Failure

Early Syphilis

• Serologic testing at 6 and 12 months 1
• HIV-infected: 1,2,3,6,9, and 12 months 3
• Treatment failure criteria: Fourfold increase in titers, failure of initially high titer (≥1:32) to decline fourfold within 12-24 months, or new clinical symptoms 5, 1

Late Latent Syphilis

• Serologic testing at 6,12,18, and 24 months 5
• Same treatment failure criteria apply 1

Management of Treatment Failure

• Perform CSF examination 5, 1
• Re-treat with benzathine penicillin G 7.2 million units (three weekly doses) if CSF is normal 5, 1
• Treat as neurosyphilis if CSF abnormalities present 5, 1

Critical Caveats

Benzathine penicillin G shortages: Ongoing global supply issues necessitate awareness of alternative regimens, though penicillin remains superior 8, 9, 10

Serofast state: A significant proportion of patients remain seropositive after treatment; this does not necessarily indicate treatment failure if titers have declined appropriately 1, 2

Serologic response timing: Expect response by 6 months for early syphilis but 12-24 months for latent syphilis 2

Partner notification: All sexual contacts within 90 days for primary syphilis, 6 months for secondary, and 1 year for early latent must be evaluated and treated 1

Prevention strategies: Doxycycline 200 mg within 72 hours after sex as post-exposure prophylaxis is recommended for MSM and transgender women with recent STI history 11, 8, 9