Secnidazole (trade names Flagentyl, Sindose, Solosec) is a nitroimidazole derivative used to in the treatment of amoebiasis and bacterial vaginosis. Secnidazole and other 5-nitroimidazole drugs enter micro-organisms by passive diffusion and undergo activation by reduction of the 5-nitro group. In anaerobic micro-organisms, such as Trichomonas, Giardia and Entamoeba spp., this intracellular reduction occurs via the pyruvate ferredoxin oxidoreductase complex and results in a concentration gradient across the cell membrane which, in tum, enhances transport of the parent drug into the cell. Because the electron affinity of the 5-nitroimidazoles is greater than that of reduced ferredoxin, the drug interrupts the normal electron flow. Aerobic micro-organisms have a more positive redox potential (i.e. are more efficient electron acceptors) than secnidazole and other 5-nitroimidazoles, which explains the selective toxicity of these drugs against anaerobic microorganisms. DNA is the intracellular target of the Secnidazole and other 5-nitroimidazoles. Secnidazole and other 5-nitroimidazoles possess selective activity against many anaerobic Gram-positive and Gram-negative bacteria and protozoa. In general, secnidazole and metronidazole were approximately equipotent in activity against Bacteroides fragilis, Trichomonas vaginalis, and Entamoeba histolytica, in in vitro studies. Secnidazole is rapidly and completely absorbed after oral administration. Plasma drug concentrations are linear over the therapeutic dose range of 0.5 to 2g. The tolerability profile of secnidazole does not differ markedly from other 5-nitroimidazoles. The most commonly reported adverse events in clinical trials involved the gastrointestinal tract (nausea, vomiting, glossitis, anorexia, epigastric pain and a metallic taste) and occurred in 2 to 10% of patients. A headache and dizziness were experienced by about 2% of patients. The drug was equally well tolerated in adults and children, and no adverse event required therapeutic intervention or treatment withdrawal.

Ornidazole is nitroimidazole derivative. It is an antiprotozoal drug that has proven to be effective against Trichomonas vaginalis, Entoamoeba histolytica, Giardia lamblia and Helicobacter pylori. The reduction of the nitro group and the generation of short-lived reactive intermediates are the basis of its parasiticidal activity. Ornidazole is a DNA-tropic drug with selective activity against microorganisms with enzyme systems capable of reducing the nitrogroup and catalyze the interaction between ferrodoxin proteins and nitrocompounds. After the drug penetrates the microbial cell, the mechanism of its action is based reducing the nitrogroup under the influence of the microorganism’s nitroreductases and the activity of the reduced nitroimidazole. The reduction products create compounds with DNA causing it to degrade, and disrupt the DNA replication and transcription processes. Furthermore, the drug’s metabolism products have cytotoxic properties and disrupt cellular respiration processes. It is indicated for the treatment of anaerobic systemic infections caused by ornidazole-sensitive microflora, prevention of infections caused by anaerobic bacteria, during operative treatment (especially middle and straight intestine surgeries), gynecological surgeries, severe intestinal ameobiasis, all extra-intestinal ameobiasis forms, giardiasis. Ornidazole was shown to be effective for the prevention of recurrence of Crohn's disease after ileocolonic resection.