Treatment

Syphilis is normally treated with a course of antibiotics. Historically, syphilis treatment has had a higher failure rate in HIV-positive people. A retrospective study involving 129 HIV-positive and 168 HIV-negative individuals diagnosed with primary, secondary and latent syphilis between 1992 and 2000 found that treatment for syphilis failed serologically in 29 HIV-positive and seven HIV-negative individuals. However, in seven HIV-positive and two HIV-negative patients this treatment failure was due to reinfection with syphilis. HIV-positive people were six times more likely to experience failure of syphilis treatment.1

A study comparing HIV-infected and uninfected people with syphilis found the HIV group had a poorer serological response but clinical failures were rare.2

In HIV-positive people, syphilis is usually treated with high doses of antibiotics such as penicillin, benzylpenicillin (Crystapen) or doxycycline (Vibramycin / Vibramycin D). A single injection of benzylpenicillin, which remains active for weeks, is usually sufficient to cure syphilis, although some doctors prescribe a course of injections over three weeks. It is usually injected into the buttocks.

WHO's preferred treatment for all forms of syphilis is penicillin. Only if patients are allergic to penicillin should other treatments be given. There is some evidence that ceftriaxone (Rocephin) is also an effective treatment for neurosyphilis in HIV-infected people.3

However, the only set of guidelines developed specifically for HIV-positive people, which were last updated in 2006 by the HIV Special Interest Group of the British Association of Sexual Health and HIV (BASHH), recommend two doses of intramuscular benzathine penicillin G one week apart to treat syphilis.

Since the 1990s, the oral antibiotic azithromycin (Zithromax) has been used by some doctors to treat syphilis. A single dose of 2g is sufficient to cure the condition, and it has the added benefit of being active against other sexually transmitted infections such as Chlamydia. However, there have been recent reports of azithromycin resistant syphilis in gay men in San Francisco, Baltimore, Seattle, and, notably, Dublin, where 88% of samples analysed were found to be resistant to the drug.4 There have been no reports of penicillin-resistant syphilis.

Treatment for neurosyphilis is similar to that for primary syphilis. Three markers are usually used to assess the effectiveness of treatment: VDRL reactivity, as well as levels of CDF protein and white blood cells in the CSF should normalise within six months of antibiotic therapy. Recently, concern has been raised about the reliability of these markers in HIV-positive patients, particularly those with low CD4 cell counts, due to a higher false positive rate.5 However, it remains uncertain whether this reflects a need for more aggressive treatment in neurosyphilis patients with HIV.

Neurosyphilis may occur without other symptoms of primary infection, and may also persist despite treatment with benzathine penicillin in HIV-positive patients.

References

  1. Ghanem KG et al. Ghanem KG et al. Serological response to syphilis treatment in HIV infected and uninfected patients attending STD clinic. Sexually Transmitted Infections 83(2):97-101, 2007
  2. Rolfs RT et al. A randomized trial of enahnced therapy for early syphilis in patients with and without human immunodeficiency virus infection. New England Journal of Medicine 337(5): 307-314, 1997
  3. Marra CM et al. A pilot study evaluating ceftriaxone and penicillin G as treatment agents for neurosyphilis in human immunodeficiency virus-infected individuals. Clinical Infectious Diseases 30(3): 540-544, 2000
  4. Lukehart SA et al. Macrolide resistance in Treponema pallidum in the United States and Ireland. N Engl J Med 351: 154-158, 2004
  5. Marra CM et al. Normalization of cerebrospinal fluid abnormalities after neurosyphilis therapy: does HIV status matter? Clin Infect Dis 38: 1001-1006, 2004
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