What is the primary treatment for a patient with new onset syphilis?

Primary Treatment for New Onset Syphilis

The primary treatment for new onset syphilis is benzathine penicillin G 2.4 million units administered intramuscularly in a single dose. 1

Treatment Recommendations by Stage

Early Syphilis (Primary, Secondary, and Early Latent)

• First-line treatment: Benzathine penicillin G 2.4 million units IM in a single dose 1
• This recommendation is supported by more than 40 years of clinical experience 2
• Treatment success rates range from 90% to 100% 3

Alternative Treatments for Penicillin-Allergic Patients (Non-Pregnant)

• Doxycycline 100 mg orally twice daily for 14 days 1, 4
• Tetracycline 500 mg orally four times daily for 14 days 1
• Ceftriaxone 2 grams daily either IM or IV for 10-14 days (with caution) 1

Special Considerations

HIV Co-infection

• Patients with HIV infection who have early syphilis should be managed according to standard treatment recommendations 2
• However, they may be at increased risk for neurologic complications and may have higher rates of treatment failure 2
• More intensive monitoring is recommended with clinical and serological evaluation at 3 and 6 months after treatment 1

Penicillin Allergy Management

• For patients with severe penicillin allergy, especially pregnant women or those with neurosyphilis, desensitization followed by standard penicillin treatment should be considered 1
• In non-pregnant patients with no evidence of CNS involvement, doxycycline is the preferred alternative 4, 5

Treatment Response Monitoring

• Clinical and serological evaluation should be performed at 3 and 6 months after treatment 1
• Treatment success is defined as a four-fold decrease in non-treponemal test titers within:
  • 6 months for early syphilis 1
  • 12-24 months for latent syphilis 1, 3

Administration Tips

• The IM administration of penicillin G benzathine diluted with 1% mepivacaine induces significantly less immediate local pain compared to penicillin G benzathine alone 6
• Needle gauge (19G vs 21G) does not significantly affect pain during administration 6

Common Pitfalls and Caveats

• Benzathine penicillin G shortages have been reported, potentially requiring temporary use of alternative regimens 7
• The "serofast state" (persistent positive serology despite adequate treatment) occurs in a significant proportion of patients and should not be confused with treatment failure 3
• Patients with high initial serologic titers may become seronegative more slowly than those with low pretreatment titers 8
• Partner notification and treatment is essential for preventing further transmission 1
• HIV testing should be performed in all patients with syphilis 1