Drugs in this class are used for: Treatment and/or prophylaxis of infections
Metronidazole is an antiprotozoal and antibacterial medication used to treat anaerobic infections, protozoal infections, Helicobacter pylori eradication and susceptible skin infections. Metronidazole is bactericidal and its mechanism of action is more likely to be attributable to the disruption of existing bacterial DNA and inhibition of its synthesis in prone organisms. Metronidazole is selectively taken up by such organisms due to the ability of these organisms to reduce metronidazole to its active form intracellularly.
Dosage regimen
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Use |
Dosage |
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Anaerobic infections (usually treated for 7 days and for 10-14 days in Clostridium difficile infection) |
By mouth: either 800mg initially then 400mg every 8 hours or 500mg every 8 hours By rectum:1g every 8 hours for 3 days, then 1g every 12 hours By IV infusion: over 20mins, 500mg every 8 hours
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Leg ulcers and pressure sores |
By mouth: 400mg every 8 hours for 7 days
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Bacterial vaginosis |
By mouth: 400-500mg twice daily for 5-7 days or 2g as a single dose
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Pelvic inflammatory disease |
By mouth: 400mg twice daily for 14 days
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Acute ulcerative gingivitis |
By mouth: 200-250mg every 8 hours for 3 days
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Acute oral infections |
By mouth: 200mg every 8 hours for 3-7 days
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Surgical prophylaxis |
By mouth: 400-500mg 2 hours before surgery; up to 3 further doses of 400-500mg may be given every 8 hours for high-risk procedures |
Please refer to SPC for children’s doses.
Patient knowledge
• Medication should be taken with or after food to reduce chances of gastrointestinal disturbances.
• Complete the course to optimise treatment success and to reduce chances of resistance.
• Must avoid consumption of alcohol while taking metronidazole as it causes a disulfiram-like reaction (this can include; nausea, vomiting, flushing of the skin, tachycardia, shortness of breath). The half-life of Metronidazole is about 8 hours, so avoid consumption during the treatment and at least 1-2 days after the course has been completed.
• Metronidazole may reduce contraceptive effect of hormonal contraceptives. Therefore patients need to be aware that additional contraception may need to be used (e.g. condoms) to prevent pregnancy.
• In addition to those discussed above, a patients current medication will need to be checked as metronidazole can interact with drugs such as; anticoagulants, phenytoin, barbiturates, disulfiram, lithium and cimetidine.
Is the medicine working?
• Most infections only need metronidazole between three and seven days but if infections are recurrent perhaps patient compliance to medicines needs to be analysed.
• Assessment of possible swallowing difficulties should be analysed. Pharmacists can acquire syrup forms of the metronidazole.
Side effects
• Gastro-intestinal disturbances (eg nausea, vomiting)
• Taste disturbances
• Furred tongue
• Oral mucositis
• Anorexia
• Hypersensitivity reactions (eg rashes and anaphylaxis)
Monitoring
• Those that are taking metronidazole for more than ten days are advised to undergo clinical and laboratory monitoring. Tests may include liver function tests, white blood cell counts or even check for side effects. It is important that patients keep all doctor and lab appointments for that their condition can be checked regularly.
• Compliance assessment (eg conduct monthly tablet counts).
Lifestyle
• Maintain a varied, healthy diet to build up the immune system. Ensure adequate hydration (especially in the elderly and children).
• Encourage compliance to minimise risk of resistance.