difficile is an anaerobic Gram-positive organism that causes diarrhoea, which in some cases can be severe. Metronidazole 400 mg, three times per day, for ten to fourteen daysĬ. Unlike metronidazole, ornidazole does not interact with alcohol (See below), but it does potentiate the effect of warfarin. It is administered as a single dose of 1.5 g or 500 mg, twice daily, for five days. Ornidazole has similar antimicrobial activities to metronidazole and is an effective alternative in the treatment of bacterial vaginosis. Treating the male sexual partner of a woman with bacterial vaginosis is unnecessary because there is no evidence that it reduces the risk of relapse. 7 The seven day course of metronidazole is also recommended in women who are breast feeding to reduce the concentration in the breast milk. 6 The seven day course is more appropriate for pregnant women because single dose regimens may result in higher serum concentrations, which can reach the foetal circulation. One study found that symptoms had resolved in 62% of women three to four weeks after the single-dose course and in 82% after the seven day course. A seven day course of metronidazole is now favoured as it is more effective than the single dose regimen for resolving symptoms, although compliance may be an issue. Metronidazole 400 mg, twice daily, for seven days OR a single dose of metronidazole 2 g (5 x 400 mg tablets)īacterial vaginosis results from the replacement of normal vaginal flora by anaerobic bacteria such as Gardnerella, Bacteroides and Mobilunculus species. Studies carried out in New Zealand have shown that anaerobic bacteria are still mostly susceptible to metronidazole and it remains a good empirical choice for suspected anaerobic infections. However, Propionibacterium propionica and approximately 70 – 75% of Actinomyces species are resistant to metronidazole.Īnaerobic infections are usually treated empirically, without susceptibility testing. 2ĭespite extensive use worldwide, acquired resistance to metronidazole among anaerobic bacteria is rare.
Gram-negative anaerobic bacteria, such as those belonging to the Bacteroides fragilis group and Gram-positive anaerobic bacteria such as Peptostreptococcus and Clostridium species, are also usually sensitive to metronidazole. Metronidazole is active against most anaerobic protozoa including Giardia lamblia, Trichomonas vaginalis, Entamoeba histolytica and Blastocystis hominis. Its mechanism of action is not entirely clear, but it is thought that the active metabolite interferes with DNA synthesis.
Metronidazole is a core antibiotic for the treatment of anaerobic infections.