Single dose of benzathine penicillin effective against early syphilis
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Key takeaways:
- In most cases, a single BPG dose is as effective against early syphilis as a three-dose regimen.
- Syphilis rates increased by 28.6% from 2020 to 2021, according to the CDC.
BOSTON — A single dose of benzathine penicillin G is effective against early syphilis regardless of HIV status, according to a study presented at IDWeek.
Edward W. Hook III, FIDSA, emeritus professor of medicine at the University of Alabama at Birmingham, and colleagues compared a single dose of benzathine penicillin G (BPG) to three doses given weekly in patients with early syphilis, finding that a single dose was effective more often and resulted in less pain and tenderness at the injection site, according to the study.
In 2021, more than 176,000 cases of syphilis were reported in the United States, including nearly 54,000 cases of primary and secondary syphilis, according to the CDC. Although U.S. rates reached historic lows in 2000 and 2001, they have increased every year since — including a 28.6% leap from 2020 to 2021 — the agency reported.
“Syphilis is an emerging problem — an old problem that’s getting worse and not better,” Jodie A. Dionne, MD, MSPH, associate professor of medicine at the University of Alabama at Birmingham, said during a presentation at IDWeek.
“In our clinics, we’ve had more than a decade of steadily increasing rates, initially among men who have sex with men, but more recently, congenital infections [and] people with opposite sex partners, and we need to find some ways to turn this around,” Dionne said.
The CDC recommends a single injection of long-acting BPG, noting it can cure early syphilis, including primary, secondary and latent infections, and three BPG doses at 1-week intervals for more serious infections, including late latent syphilis and latent syphilis of unknown duration.
According to Dionne, however, surveys have shown clinicians defaulting to a three-dose BPG regimen for most syphilis infections regardless of infection duration. Additionally, amid a shortage of BPG and restrictions on its use, there have been questions about a single BPG dose’s effectiveness in people with HIV who have an early syphilis coinfection, she said.
Hook and colleagues enrolled 249 participants at 10 sites in a multicenter randomized controlled trial comparing a single 2.4 million-unit BPG injection to three injections administered in successive weeks among people living with and without HIV.
Among the participants, 97% were male, 62% were Black and 64% were living with HIV. Syphilis stage distribution among study participants was 19% primary, 47% secondary, 33% early latent and did not differ by HIV status, according to the study.
Among people both with and without HIV, the researchers found no difference in rapid plasma reagin response, which was 73% in the single-dose group and 74% in the three-dose group.
Overall, Dionne called response rates among participants in both study groups “remarkably the same” and, irrespective of HIV infection status, “we are able to say, with this randomized controlled study, there was no significant difference in treatment response at 6 months.”
Most study participants — 81%, according to Dionne — experienced mild to moderate pain and tenderness at the injection site, which she said is an additional reason to use a single-injection regiment when appropriate.
“Anecdotally, in our clinic, we had several patients who were eligible [for the study] who I tried to enroll, and they said ‘doc, I would never take three doses if I didn’t have to take three doses of this drug,’” Dionne said.
She noted a primary study endpoint of cure at 6 months but added that 12-month data are being collected and analyzed, and are on the way.
“Treatment of persons with early syphilis with more than a single dose of 2.4 million units of BPG offers no therapeutic benefit irrespective of HIV infection status and was associated with increased rates of injection site discomfort,” the researchers concluded.
References:
- Hook EW, et al. Abstract 2889. Presented at: IDWeek; Oct. 11-15, 2023; Boston.
- CDC. Sexually transmitted diseases (STDs): Syphilis treatment and care. https://www.cdc.gov/std/syphilis/treatment.htm. Last reviewed Aug. 11, 2023. Accessed Oct. 27, 2023.
- CDC. Sexually transmitted disease surveillance 2021: National overview of STDS, 2021. https://www.cdc.gov/std/statistics/2021/overview.htm. Last reviewed May 16, 2023. Accessed Oct. 27, 2023.
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Hook EW, et al. Abstract 2889. Presented at: IDWeek, Oct. 11-15, 2023; Boston.
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