Treatment of Primary Syphilis with Leg Chancre
For a patient with a chancre on the leg present for approximately one month, consistent with primary syphilis, treat immediately with benzathine penicillin G 2.4 million units intramuscularly as a single dose. 1
Immediate Treatment Approach
Benzathine penicillin G 2.4 million units IM in a single dose is the definitive treatment for primary syphilis, with four decades of documented efficacy in achieving local cure and preventing late sequelae. 1
Treatment should not be delayed while awaiting confirmatory testing, as the chancre timing (one month duration) is classic for primary syphilis. 1
Essential Pre-Treatment Evaluation
Test for HIV infection immediately, as all patients with syphilis require HIV testing, and HIV-positive patients need more intensive monitoring. 1, 2
Perform serologic testing with nontreponemal tests (RPR or VDRL) to establish baseline titers for monitoring treatment response. 3
Do NOT perform lumbar puncture unless the patient has neurologic symptoms (headache, vision changes, hearing loss, cranial nerve deficits) or ophthalmic symptoms (uveitis), as CSF invasion is common in early syphilis but rarely leads to neurosyphilis with standard treatment. 1
Alternative Regimens for Penicillin Allergy
If the patient has documented penicillin allergy:
Doxycycline 100 mg orally twice daily for 14 days is the preferred alternative for non-pregnant patients. 1, 4
Tetracycline 500 mg orally four times daily for 14 days is an option, though compliance is typically worse than with doxycycline. 1
Important caveat: Erythromycin is less effective and should only be used when compliance with therapy and follow-up can be assured. 1
For pregnant patients with penicillin allergy, desensitization followed by penicillin treatment is mandatory, as penicillin is the only documented effective therapy during pregnancy. 1
Critical Follow-Up Protocol
Structured monitoring schedule:
Re-examine clinically and serologically at 3 months and 6 months after treatment. 1
HIV-infected patients require more frequent monitoring at 3-month intervals (3,6,9, and 12 months). 2, 3
Use the same nontreponemal test (RPR or VDRL) from the same laboratory for all follow-up, as results are not interchangeable between methods. 3
Treatment Failure Indicators
Treatment failure should be suspected if:
Nontreponemal titers fail to decline fourfold by 6 months after therapy. 1, 3
A sustained fourfold increase in titer occurs compared to baseline. 1, 3
Management of treatment failure:
Re-evaluate for HIV infection. 1
Perform lumbar puncture unless reinfection is certain. 1
Re-treat with benzathine penicillin G 2.4 million units IM weekly for 3 consecutive weeks, unless CSF examination indicates neurosyphilis. 1
Partner Management
Sexual contacts require evaluation and presumptive treatment:
Treat all sexual partners from the past 3 months plus duration of symptoms presumptively, even if seronegative, as they may be infected despite negative serology. 1
Partners exposed more than 90 days before diagnosis should be treated presumptively if serologic results are unavailable immediately or follow-up is uncertain. 1
Common Pitfalls to Avoid
Jarisch-Herxheimer reaction occurs within 24 hours in many patients with early syphilis—warn the patient to expect fever, headache, and myalgia, which can be managed with antipyretics. 1
Do not use treponemal tests (FTA-ABS, TPHA) to monitor treatment response, as they remain positive for life regardless of treatment success. 3
A fourfold change in titer equals two dilutions (e.g., 1:32 to 1:8), not a simple multiplication by four. 3
Never use single-dose ceftriaxone, as it is ineffective for treating syphilis despite being effective for chancroid. 1