Tinidazole: Another Therapeutic Option for Syphilis?

After the incidental observation of an almost complete resolution of maculopapular eruption in a patient having simultaneously secondary syphilis and trichomonas vaginalis infection, we extended the treatment with tinidazole (500 mg 4 times daily for 7 days) to 10 other early syphilis patients before the start of the conventional penicillin treatment. All patients showed marked improvement of their lesions in a few days. After the introduction of the conventional penicillin regimen, the lesions further improved and VDRL titers declined at least 4-fold within 6 months in all patients. Tinidazole is a 5-nitroimidazole derivative as well as metronidazole but with a longer plasma half-life. It is activated intracellularly by bacterial/parasitic enzymes to a redox cytotoxic intermediate that damages large protein molecules and inhibits repair and transcription of DNA affecting also the cell wall. With this action, tinidazole might also have a synergic action with penicillin and doxycycline, facilitating the entry of such drugs. It is possible that tinidazole has the same bactericidal action on spirochetes other than Borrelia, such as Treponema pallidum, explaining its rapid therapeutic action on the lesions of early syphilis. Whether this action could be confirmed by studies on larger series of patients, tinidazole might be considered in case of allergy to penicillin or other antibiotics usually prescribed in syphilis.