Comparisons of Treatment Responses of Early Syphilis to Benzathine Penicillin G With or Without Doxycycline

This study compares two antibiotic treatments — benzathine penicillin G alone vs. benzathine penicillin G plus doxycycline — for treating early syphilis in people living with HIV (PLWH). Syphilis can be harder to treat in people with HIV, and this study aims to find the most effective approach. **You may be eligible if...** - You are living with HIV and are 18 or older - You have been diagnosed with early syphilis (primary, secondary, or early latent) - Your syphilis has been confirmed by a positive RPR blood test with a reactive TPPA assay - Your RPR titer is 4 or higher **You may NOT be eligible if...** - Your RPR titer is below 4 - You have taken antibiotics active against syphilis in the past 4 weeks - You have another concurrent infection (like chlamydia or Mycoplasma genitalium) that requires overlapping antibiotic treatment with syphilis-active drugs Talk to your doctor to see if this trial is right for you.