Metronidazole has been used for the treatment of infections for 145 years and is still successfully used for
the treatment of trichomoniasis, amoebiasis, and giardiasis. Anaerobic bacterial infections caused by Bacteroides
species, fusobacteria, and clostridia respond favorably to metronidazole therapy. Good clinical results in
the treatment of vaginosis due to Gardnerella vaginalis have also been reported. Rates of resistance to metronidazole
are still generally low; however, several studies have reported decreased susceptibility among Bacteroides
species, as well as different mechanisms of resistance. Metronidazole-resistant Helicobacter pylori
strains have been described, but combination therapy (eg, metronidazole, amoxicillin, or clarithromycin plus
omeprazole) is still recommended for eradication of this pathogen in patients with gastroduodenal ulcers.
Metronidazole is considered to be a cost-effective drug because of its low cost, good activity against pathogenic
anaerobic bacteria, favorable pharmacokinetic and pharmacodynamic properties, and minor adverse effects.
Metronidazole is still the criterion standard for therapy of anaerobic infections, as was described by Tally and
colleagues 35 years ago.