Penicillin concentrations in cerebrospinal fluid after different treatment regimens for syphilis.

Abstract

The concentrations of penicillin in the CSF were compared simultaneously with those in the serum in 17 patients with late secondary or neurosyphilis. The antibiotic concentrations were measured by the agar well diffusion method. There were no detectable concentrations of penicillin in the CSF after administration of 2.4 or 7.2 MU of benzathine pencillin, 12 MU of procaine penicillin in aluminum monostearate or 2.4 MU of aqueous procaine penicillin G. Only after high doses (24 MU daily) of aqueous penicillin G (APG) or after a combination of 2 MU APG plus 2 g oral probenecid daily was penicillin detectable in the CSF. Concentrations after the latter regimen were higher and greatly exceeded the minimum inhibitory concentration for Treponema pallidum.