Penicillin levels in blood and CSF achieved by treatment of syphilis.

Treponemicidal levels of penicillin in the CSF were not obtained following intramuscular (IM) injections of 600,000 IU of penicillin G procaine along with 2% aluminum monostearate (PAM). Treponemicidal levels of penicillin in the CSF were achieved in 31 patients by probenecid, 500 mg/6 hr by mouth, with penicillin G, 500,000 IU by IM injection, and by probenecid every six hours by mouth and IM injections of penicillin G procaine once a day in two of three patients following injections of 600,000 IU, in four of five following 1.2 million IU, and in three (now all nine) following 2.4 million IU.