Patients with HIV Infection, Early Syphilis Benefit from Single Dose of Benzathine Penicillin

SAN FRANCISCO, CA—A single dose of benzathine penicillin G is sufficient to treat patients with HIV infection and early syphilis, a study presented at IDWeek 2013 has found.

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These results support current treatment guidelines, which recommend the use of 2.4 million units of benzathine penicillin G for the treatment of primary, secondary, and early latent syphilis in persons with HIV infection; “however, compliance with this recommendation is variable,” said Anuradha Ganesan, MBBS, MPH, of the Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, and Walter Reed National Military Medical Center, Bethesda, MD.

To assess the adequacy of this recommendation, Dr. Ganesan and colleagues examined syphilis treatment responses and factors associated with response in the US Military HIV Natural History Study, a well-characterized cohort of Department of Defense beneficiaries.

For this study, visits occurred every 6 months. Participants were interviewed by research staff to determine history of sexually transmitted infections and treatment of syphilis. Blood was drawn and a physician performed an evaluation for signs and symptoms of disease.

The study included subjects with early syphilis if they met serologic criteria for syphilis, defined as a positive non-treponemal (NTr) test confirmed by treponemal (Tr) testing. Participants also had to have treatment documented and follow-up NTr titers drawn within 12 months of treatment. A given individual could contribute more than one case.

“We defined syphilis episodes as being early if the subject had a negative NTr test in the 365 days prior to their positive NTr test,” Dr. Ganesan reported. “Response to treatment was assessed at 12 months.” Serologic response was defined as a ≥4-fold decline in NTr titer following treatment.

Of the 5679 participants in the Natural History Study, 741 subjects met the serologic criteria for syphilis, contributing 1038 cases. Of these, 616 cases had early syphilis (n=439), 541 cases (n=394) were treated, and 453 cases (n=335) had a known response: 411 responded and 42 did not. The subjects were 99% male and 63% African American.

Of the 453 cases, 130 (29%) received one dose of benzathine penicillin G; 239 (53%), ≥2 doses of benzathine penicillin G; and 84 (10%) received other treatment (eg, a nonpenicillin-containing regimen). The majority of the cases (68%) had HAART use and 55% were virologically suppressed.

Overall, more than 90% of persons with HIV infection responded to treatment. Factors significantly associated with serological response were age (per 10-year increase; P=0.003) and NTr titer ≥1:64 (P<0.001). Risk factors associated with serologic failure included older age and lower pretreatment rapid plasma reagin titers.

Dr. Ganesan said, “Study limitations included that it was a retrospective design and 25% of the cases were excluded.” She also noted a recent shift in practice patterns in the Natural Health Study, with a majority of providers favoring a single dose of benzathine penicillin G for the treatment of early cases of syphilis.