Ceftriaxone given repeatedly cures manifest syphilis in the rabbit.

Repeated intramuscular injection of ceftriaxone to rabbits with manifest syphilitic orchitis leads to clinical cure as does penicillin, given the serum levels reached are similar to the ones obtained clinically in man. Totally different to untreated controls the Treponema pallidum hemagglutination (TPHA) titers remain relatively low and later even tend to decrease further. Thus, it seems justified to start clinical trials on the definite role of ceftriaxone in the treatment of clinical syphilis.