One vs three weekly doses of benzathine penicillin G for treatment of early syphilis in persons with and without HIV: a multicenter randomized controlled trial
Presenter: Jodie A. Dionne, MD, University of Alabama at Birmingham, AL, United States
In a randomized, controlled trial, treating early syphilis with more than a single dose of benzathine penicillin G offered no advantage over giving a single dose, irrespective of the patient’s HIV status, stated Jodie A. Dionne MD, University of Alabama at Birmingham, AL, United States, in an ID Week 2023 oral presentation.
For more than a decade now, syphilis rates have been steadily increasing in the United States. While most cases were initially among men who have sex with men, more recently clinicians have been seeing congenital infections and infections among persons with opposite-sex partners. Rates of HIV co-infection are high, Dionne noted. Although benzathine penicillin G has been the treatment of choice for more than 75 years, controversy remains over the optimal duration of treatment for patients with early (primary, secondary, or early latent) syphilis, particularly for those co-infected with HIV. Ongoing national shortages of this drug make determining optimal duration of therapy an urgent concern, Dionne emphasized.
To compare the efficacy of a single dose of 2.4 million units of benzathine penicillin G vs 3 weekly doses a week apart for treatment of early syphilis in persons with and without HIV, Dionne and colleagues designed a noninferiority trial with a 10% margin, estimating a response rate of 69% with 1 dose and 79% with 3 doses. They enrolled 249 adult nonpregnant participants with untreated primary, secondary, or early latent syphilis at 10 participating sites. The main outcome measure was response to therapy at 6 months (rapid plasma reagin [RPR] titer compared with baseline RPR). A “cure,” Dionne said, was defined as an RPR titer at the 6-month visit that was 2 or more dilutions (4-fold) lower than the initial RPR titer. Nonresponse was defined as an unchanged RPR titer or plus or minus 1 dilution at 6 months. Any increase in RPR titer, even if transient, was considered a treatment failure.
The mean age of the participants was 35 years, 97% were men, 62% were Black, and 61% were living with HIV. The syphilis stage distribution was 19% primary, 47% secondary, and 33% early latent, with no significant differences according to HIV status. The primary outcome of the study was a 4-fold or greater decline in RPR titer measured at 6 months.
Reporting outcomes, Dionne noted that with per protocol and intention-to-treat analysis revealing no differences, she would report intention-to-treat findings only. The rate of serologic response (≥ 4-fold decline in RPR titer) at 6 months in the single-dose group was 76% (95% confidence interval [CI] 0.68–0.82), which did not differ significantly from the 3-dose group rate (70%, 95% CI 0.61–0.77). There were no treatment failures (≥ 4-fold increase in RPR titer). Similarly, there was no significant difference in RPR response at 6 months between persons with HIV (73%) and without HIV (74%). Mild-to-moderate local injection site pain and tenderness was reported by 81% of participants, Dionne said.
Concluding, Dionne stated that treating early syphilis with more than a single dose of 2.4 million units of benzathine penicillin G, regardless of HIV status, offers no therapeutic benefit. “There is no significant difference in the serological response to treatment among persons with and without HIV,” she said.
Disclosures. Funding was through STI CTG HHSN2722013000121.
Dr. Dionne had no disclosures.