Prophylactic Treatment for Syphilis Exposure
This patient should receive presumptive treatment with benzathine penicillin G 2.4 million units IM as a single dose immediately, even though his current RPR test is negative. 1
Rationale for Presumptive Treatment
The CDC explicitly recommends presumptive treatment for sexual partners of syphilis patients who were exposed within 90 days prior to the partner's diagnosis, regardless of serologic test results. 1 This patient's exposure occurred within the past 6 months, and his partner was treated for syphilis just 2 months ago, placing him squarely within the high-risk window. The key principle here is that early syphilis infection may not yet produce detectable antibodies, making seronegative results unreliable for ruling out infection in recently exposed individuals. 1
Treatment Regimen
Benzathine penicillin G 2.4 million units IM in a single dose is the recommended prophylactic treatment—identical to the regimen used for primary and secondary syphilis. 1, 2
This patient has no penicillin allergy, making this the straightforward first-line choice. 2
The single-dose regimen provides adequate treponemicidal blood levels and prevents progression to symptomatic disease. 2
Alternative Regimens (If Penicillin Allergy Were Present)
If this patient had a penicillin allergy, the recommended alternative would be:
Tetracycline 500 mg orally four times daily for 2 weeks is an alternative, though compliance is typically better with doxycycline. 2
Erythromycin 500 mg orally four times daily for 2 weeks is less effective and should only be used when compliance can be assured. 2
Critical Follow-Up Requirements
Repeat serologic testing (RPR or VDRL) at 6,12, and 24 weeks after exposure is essential, as initial negative tests do not exclude early infection. 2
All patients with syphilis exposure should be tested for HIV, as co-infection is common. 2, 1
The patient should be counseled to abstain from sexual intercourse until treatment is completed and to return immediately if any symptoms develop (painless ulcers, rash, lymphadenopathy). 2
Important Clinical Caveats
Do not rely on negative serologic tests alone in recently exposed contacts—the window period for antibody development can extend beyond initial testing. 1
The Jarisch-Herxheimer reaction may occur within 24 hours of penicillin treatment, presenting with fever, headache, and myalgias; patients should be counseled about this possibility. 1
Early treatment prevents progression to later stages of syphilis that cause significant morbidity (cardiovascular syphilis, neurosyphilis, gummatous disease) and mortality. 1
For secondary syphilis contacts, the CDC recommends identifying partners from 6 months plus duration of symptoms before treatment; for early latent syphilis, this extends to 1 year. 1 This patient's 6-month exposure window with a partner treated 2 months ago falls within these guidelines.