Biopharmacology of syphilotherapy.

Data collected from experimental rabbit syphilis and from in vitro studies with nonpathogenic treponemes can be extended only with great caution to human syphilis. The following tentative conclusions may be drawn: penicillin acts on Treponema pallidum by interfering with cell wall synthesis. Concentrations of penicillin greater than 0.1 mug/ml do not have increased treponemicidal effect. Regimens producing penicillinemia for at least 8 days are considerably more efficient than treatment yielding high peak serum levels of brief duration. Treponemal residence in antibiotic-protected sites increases the need for long duration therapy. Other antibiotics are less effective than penicillin, and patterns of antibiotic interaction against treponemes do not match those seen with other bacteria.