日本性感染症学会誌 Journal of Japanese Society for Sexually Transmitted Infections

Since March 2022, intramuscular injection of benzylpenicillin benzathine hydrate (PCG benzathine) has been the first-line treatment for syphilis at our hospital. This study was conducted to investigate whether PCG benzathine provides superior outcomes than alternative treatments. From January 2019 to February 2025, Group A (16 patients) was treated with oral amoxicillin hydrate (1500 mg/day), and Group P (24 patients) was treated with intramuscular PCG benzathine. Among these 40 patients, 31 were diagnosed with early syphilis, 3 had reinfection, and 9 had late syphilis. Clinical presentations included 20 cases of latent syphilis (asymptomatic), 6 cases of condyloma latum, 5 cases each of hard chancre and eruption, and 4 cases with atypical symptoms, such as vulvar pruritus, inguinal lymphadenopathy, fever, and abdominal pain. Jarisch–Herxheimer reactions were detected in two patients in Group A and one patient in Group P. Additional treatment was required for two patients in Group A and one patient in Group P. Among 14 pregnancies complicated by syphilis, 10 resulted in artificial termination, whereas 4 (3 in Group A and 1 in Group P) resulted in normal deliveries. There were no instances of premature birth or congenital syphilis. A total of 31 cases were considered cured. However, eight cases reported unknown therapeutic effects (one in Group A and seven in Group P), of which six (one in Group A and five in Group P) were terminated without the evaluation of the initial efficacy. PCG benzathine is a valuable first-line treatment, even in patients with poor compliance, and may be continued as the standard therapy for syphilis.