Efficacy of ceftizoxime in the treatment of incubating syphilis in rabbits.

While ceftizoxime given as a single intramuscular shot cures uncomplicated gonorrhoea in almost every case, its efficacy against Treponema pallidum in cases of concomitant incubating syphilis is less clear. To analyse this question, the rabbit orchitis model was used. After initial experiments defining appropriate inocula and doses, ceftizoxime was compared to penicillin G with its well-known activity against the organism in vitro and in vivo. According to the final experiment, ceftizoxime applied in doses corresponding to the ones used in humans for uncomplicated gonorrhoea cures rabbit orchitis due to T. pallidum about as effectively as penicillin. Hence there seems to be no need to refrain from using the third-generation cephalosporin ceftizoxime to cure gonorrhoea for fear of masking concomitant syphilis.