The common clinical role of metronidazole includes the treatment of anaerobic bacteria, Trichomonas vaginalis, and amoebic protozoa. 1. Treatment of anaerobic bacteria: including anaerobic infections in various systems, such as oral cavity, respiratory tract, digestive tract, skin and other parts of the body, including infective endocarditis, sepsis and so on, metronidazole can also have a certain effect. 2. Treatment of Trichomonas vaginalis: For female genital system Trichomonas vaginalis infection, metronidazole can be used for treatment, which can play the role of anti-Trichomonas vaginalis by destroying the nucleic acid structure of the worm and damaging the DNA chain. 3. Treatment of amebic protozoa: including intestinal amebiasis, such as amebic dysentery, and extra-intestinal amebiasis, such as amebic liver abscess, cerebral amebiasis, etc., through the anaerobic environment in which nitro is reduced to amine, and acts on the microorganisms cellular components, to achieve the effect of killing the amebic protozoa. Metronidazole has certain side effects such as nausea, drowsiness, etc. It is contraindicated for those who are allergic to this drug, so it should be taken under the guidance of a doctor to avoid adverse reactions.