Penicillin concentrations in cerebrospinal fluid (CSF) during repository treatment regimen for syphilis.

Penicillin concentrations in cerebrospinal fluid (CSF) were measured in 40 asymptomatic patients with syphilis, 10 of whom had neurosyphilis. The patients were treated with 2.4 MIU procaine penicillin a day intramuscularly in combination with 500 mg probenecid every six hours orally. This intramuscular treatment regimen did not consistently yield treponemicidal penicillin concentrations in the CSF (subtreponemicidal CSF concentrations were found in 17 patients, four of whom had neurosyphilis). These data provide additional evidence that the cure of asymptomatic neurosyphilis is not guaranteed by intramuscular penicillin treatment.