About metronidazolea nitroimidazole antibiotic, anti-infective, antiprotozoal,amebicide.mechanism of action of metronidazolemetronidazole is nitro imidazoles which have broad spectrum cidal activity against protozoa and some anaerobic bacteria. its selective toxicity to anaerobic microbes involves 1. drug enters the cell by diffusion, 2. nitro group of drug is reduced by redox proteins present only in anaerobic organisms to reactive nitro radical which exerts cytotoxic action by damaging dna and other critical biomolecules. 3. dna helix destabilization & strand breakage has been observed.indications for metronidazole1.amoebiasis 2.giardiasis 3.trichomonas vaginitis 4.pseudo membranous enterocolitis 5.anaerobic bacterial infections after surgery, brain abscess, & endocarditis 6.helicobacter pylori infections 7.ulcerative gingivitis