Penicillin CSF levels following intravenous therapy in syphilitic patients.

Serum and CSF levels of penicillin have been determined in 13 syphilitic patients treated with relatively high doses of penicillin G by the intravenous route. Wide individual variability in the CSF/serum concentration ratio was observed. In all patients the concentration of the antibiotic in the CSF was equal to or greater than 0.03 IU/ml., which is considered to be the minimal therapeutic concentration. The potential clinical usefulness of different therapeutic regimens in the treatment of neurosyphilis is discussed.