Penicillin concentrations in serum and CSF during high-dose intravenous treatment for neurosyphilis.

Eight neurosyphilitic patients (two asymptomatic, six symptomatic) were treated with intravenously administered aqueous penicillin G, 0.15 million IU/kg body weight/24 hrs for 15 days. On the 8th day of treatment, penicillin concentrations were determined in serum and CSF samples collected at hourly intervals over a period of 8 hours, using a microbiological assay method. Serum concentrations ranged from 0.26 to 100 mg/l, while CSF concentrations ranged from 0.062 to 3.0 mg/l. These results indicate that, by ensuring penicillin concentrations in CSF, which are continuously above the minimal fully treponemicidal concentration during the course of treatment, this treatment regimen should provide an adequate therapy for asymptomatic and symptomatic neurosyphilis.