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METRONIDAZOLE - a patient's guide


Metronidazole is used to fight bacterial infections. This article outlines how the drug works and its potential side effects.


Flagyl, Trichozole

USE: Antiprotozoal/ antibacterial

Metronidazole is an antimicrobial agent which penetrates the infectious cell (bacteria) and damages its DNA production thereby causing bacterial cell death and fighting infection. This medicine is used for the treatment of many microbes often causing skin and soft tissue abscesses, sexually transmitted diseases (STDs), some vaginal and amoebic infections. It can be used to treat Giardia as well. Metronidazole is also indicated in post-operative bowel surgery.


  • Previous allergy to metronidazole
  • Pregnancy and breastfeeding (discuss with doctor)
  • Liver impairment (esp. alcoholics)
  • The drug can cause a severe (antabuse-type) reaction if alcohol is taken at the same time-Avoid Alcohol totally while on this medication.

Side effects:

Occasional: stomach upset, unpleasant taste in mouth and fury tongue, skin rash and fever (discontinue treatment).

Rarely: darkening of urine, headache and drowsiness.


Alcohol intolerance due to disulfiram-like reaction (psychosis reported)

Warfarin, phenytoin, cytotoxics and lithium have increased toxicity

Reduced effect with barbiturates and phenobarbitone

Patient information:

  • Follow instructions carefully on the label of the medicine
  • Always complete the course unless directed by your doctor
  • Advise that sexual partners (in case of STDs) should seek treatment
  • Food: Take the medicine after food with a large glass of water
  • Consult your doctor or seek urgent medical help if side effects are severe or ongoing.

See also:

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