Background/introduction Benzathine penicillin G (BPG) does not cross the blood-brain barrier. Some experts believe that BPG may be ineffective when treating patients co-infected with HIV and syphilis.

Aim(s)/objectives To establish the risk of asymptomatic neurosyphilis (ANS) after treatment of early syphilis in HIV positive patients with single dose BPG.

Methods HIV patients with early syphilis were offered a post-treatment lumbar puncture if their CD4 count was <350 and/or their serum RPR >16. Patients with clinical neurosyphilis were excluded. ANS was defined as a positive CSF RPR, or CSF white blood cells >20/mm³ plus CSF TPPA >1:320.

Results 64 patients participated (median CD4 417/mm³, range 84–1100). 50 of the patients were treated with single dose BPG. Only one patient had ANS (prevalence 1.56% 95 CI 0.04–8.4) with CSF RPR negative, CSF TPPA 1:1280 and lymphocytes 45/mm³. Two patients had a pleocytosis (50 and 22 white cells/mm³ respectively) with negative CSF RPR and CSF TPPA and thus did not meet diagnostic criteria for ANS per protocol.

Discussion/conclusion Our study suggests that single dose BPG is effective treatment for early syphilis in HIV co-infected patients. We will present more data to support this conclusion.