Metronidazole Vioser (Metronidazole)

Metronidazole is used to treat infections caused by anaerobic bacteria and certain protozoa.

• Anaerobic bacterial infections: eradicates susceptible anaerobes, reducing infection severity.
• Bacterial vaginosis: restores normal vaginal flora by eliminating overgrowth of anaerobic bacteria.
• Trichomoniasis: eliminates Trichomonas vaginalis, relieving symptoms and preventing transmission.
• Amoebiasis: destroys Entamoeba histolytica trophozoites, treating intestinal and extra‑intestinal disease.
• Clostridioides difficile infection: reduces toxin‑producing C. difficile, aiding resolution of colitis.

• Metronidazole enters anaerobic microorganisms and is reduced by intracellular electron transport proteins to reactive nitro radical anions. These radicals interact with DNA, causing strand breakage and loss of helical structure, and also inhibit nucleic acid synthesis. The resulting damage leads to bacterial and protozoal cell death while sparing aerobic cells, providing selective antimicrobial activity. The drug is preferentially taken up by low‑oxygen environments, which enhances its efficacy against target pathogens.

Metronidazole may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea: mild stomach upset that may resolve without treatment.
• Metallic taste: transient metallic sensation in the mouth.
• Headache: mild to moderate headache during therapy.
• Diarrhea: loose stools that may accompany treatment.

Serious or Rare Side Effects

• Severe allergic reaction: rash, itching, swelling, or anaphylaxis requiring immediate medical attention.
• Peripheral neuropathy: tingling or numbness in extremities, potentially irreversible.
• Seizures: rare occurrence of convulsions, especially in high doses or renal impairment.
• Hepatic toxicity: elevated liver enzymes or jaundice indicating liver injury.

Before initiating Metronidazole therapy, consider the following precautions to ensure safe use.

• Renal and hepatic function: assess kidney and liver status, adjust use if impairment is present.
• Central nervous system disorders: use cautiously in patients with seizures or neuropathy history.
• Alcohol consumption: avoid alcohol during treatment and for at least 48 hours after completion to prevent disulfiram‑like reactions.
• Pregnancy and lactation: evaluate risk‑benefit, as it is classified Category B; use only if clearly needed.
• Concomitant medications: monitor for interactions that may increase toxicity or reduce efficacy.
• Store at room temperature: keep in original container, protect from light and moisture.

Metronidazole can interact with several medicines; awareness of major and moderate interactions helps manage therapy safely.

Major Interactions (Avoid)

• Alcohol: may cause severe flushing, nausea, vomiting, and tachycardia.
• Warfarin: potentiates anticoagulant effect, increasing bleeding risk.
• Lithium: may raise lithium levels, leading to toxicity.

Moderate Interactions (Monitor Closely)

• Oral contraceptives: may reduce hormonal efficacy, increasing risk of unintended pregnancy.
• Cimetidine: can increase metronidazole plasma concentrations, enhancing side effects.