Penetration of penicillin into the cerebrospinal fluid of patients with latent syphilis.

Eighteen patients with latent syphilis were treated with 360 mg, 720 mg, 1080 mg or 1440 mg intramuscular procaine penicillin daily for 14 days. Penicillin was assayed in serum and cerebrospinal fluid collected 3 hours after the second injection in each patient. Penicillin was present in all sera in concentrations greater than the generally accepted fully treponemacidal level, but none was detected in cerebrospinal fluid from 11 patients. The significance of these results is discussed, particularly with a view to changes in standard treatment regimens for latent syphilis.