Effect of unintended short-term 3.0 g/day amoxicillin and probenecid treatment for early syphilis on patients with HIV-1 infection

BACKGROUND: Standard therapy for early syphilis involves intramuscular injections of penicillin G, which frequently faces shortages in several countries. Fourteen-day amoxicillin therapy has been suggested as an alternative to benzathine penicillin G, but the optimal duration of amoxicillin therapy remains unclear and could theoretically be shortened to less than 14 days. The aim of this study was to explore the effectiveness of short-term amoxicillin therapy for early syphilis. METHODS: We retrospectively explored the effectiveness of short-term amoxicillin therapy for early syphilis. The treatment data of patients who had received amoxicillin therapy for less than 14 days for unintended reasons were reviewed. Diagnosis was confirmed based on either the physician’s description or clinical presentation. Successful treatment was defined as a fourfold or greater decline in the rapid plasma reagin titer or sero-reversion to negative within 12 months. RESULTS: Of 295 patients, 8 received short-term amoxicillin treatment. All were men who had sex with men and people living with human immunodeficiency virus. Their median age, CD4 count, and treatment duration were 34 years (range, 26–40), 258/mL (range, 112–930), and 9.5 days (range, 5–11), respectively. One patient had primary syphilis, six had secondary syphilis, and one had early latent syphilis. All patients, except one who showed reinfection, demonstrated a serological response within 4 months. The median time for serological response was 112 days. CONCLUSION: The results indicate that early syphilis could potentially be treated with 5–11 days of amoxicillin therapy combined with probenecid. This suggests that short-term amoxicillin therapy might be a sufficient treatment for early syphilis instead of the standard 14-day course.