TreatmentUpdate41: Vol. 4, No. 1 - March, 1993
Sean Hosein

According to some American doctors, in people with HIV infection who have been "successfully treated" with benzathine penicillin, the incidence of neurosyphilis (syphilis in the brain and spinal cord) is "vastly increased." The microorganism that causes syphilis, T. pallidum, can invade the brain and spinal cord shortly after infection. In the pre-AIDS era, treatment with benzathine penicillin appeared to prevent the appearance of neurosyphilis. This is interesting because the concentration of the antibiotic does not reach levels high enough to have significant anti-T. pallidum in the CSF (cerebrospinal fluid; in which the brain and spinal cord float). In some people who were infected with both HIV and T. pallidum and who received standard anti-syphilis therapy, neurosyphilis has developed. The antibiotic, ceftriaxone, is a possible treatment for HIV-infected patients who also have syphilis. Doctors in Texas have recently reported their experience using this antibiotic.

Study Details

All 56 subjects reported in this study had HIV infection as well as syphilis. These subjects had either latent syphilis or neurosyphilis. Most subjects received 1 gram (some were given 2 grams) of ceftriaxone per day given intravenously for 10 to 14 days. Others were given 1 gram/day by injections into muscles for between 10 to 14 days. Some subjects were randomly given penicillin 2.4 million units 3 times weekly. None of these subjects had sores, rashes or any other symptoms of syphilis or neuro-syphilis. In the 3 years before this study, 23 subjects had received "one to 3 doses of benzathine penicillin" as a treatment for syphilis with no symptoms of reinfection since.

Ceftriaxone: Results

Forty-three subjects received ceftriaxone. Twenty-eight of the 43 subjects who received ceftriaxone had decreased levels of antibodies against T. pallidum. The investigators described the 28 as subjects who had "responded to therapy." The decrease in antibody levels by these 28 subjects suggests that the infection was under control. In all of the remaining subjects it was not clear what happened as a result of antibiotic treatment. In 9 symptom-free subjects who did not respond, laboratory analysis of their blood suggested that one course of ceftriaxone was not useful. Seven of these 9 subjects had improved laboratory markers when they received another course of 2 grams/day of ceftriaxone for 2 weeks. One of the two subjects who did not respond to a second course of antibiotic therapy developed signs/symptoms of neurosyphilis. He was then given intravenous penicillin G in a dose of 24 million units/day for 2 weeks. However, this therapy did not improve his condition. The doctors did not provide follow-up details about what happened to this subject.

Penicillin: Results

Thirteen subjects without signs/symptoms of "active" syphilis received benzathine penicillin 2.4 million units/day 3 days for 1 week. In 8 subjects, laboratory analysis of their blood samples suggested that the infection had been brought under control. Two subjects "relapsed" despite this therapy. These 2 subjects were later given 2 grams/day of ceftriaxone for 2 weeks and responded favourably.

Referemces:

1. Dowell ME, Ross PG, Musher DM, et al. Response of latent syphilis or neurosyphilis to ceftriaxone therapy in persons infected with human immunodeficiency virus. American Journal of Medicine 1992;93:481-4?.

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